Quantitative Aptitude - SPLessons

Quantitative Aptitude Formulas Quick Read

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Quantitative Aptitude Formulas Quick Read

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Quantitative Aptitude is one of the important sections in several competitive exams across the world. Quantitative Aptitude section evaluates numerical ability and problem solving skills of candidates. This test forms the major part of a number of important entrance exams across the worldQuantitative Aptitude Formulas Quick Read article presents some of the important formulas that can be used to quickly solve the questions on any test.


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Divisibility Rules:

1. A number is divisible by 2 if it is an even number.

2. A number is divisible by 3 if the sum of the digits is divisible by 3.

3. A number is divisible by 4 if the number formed by the last two digits is divisible by 4.

4. A number is divisible by 5 if the units digit is either 5 or 0.

5. A number is divisible by 6 if the number is also divisible by both 2 and 3.

6. A number is divisible by 8 if the number formed by the last three digits is divisible by 8.

7. A number is divisible by 9 if the sum of the digits is divisible by 9.

8. A number is divisible by 10 if the units digit is 0.

9. A number is divisible by 11 if the difference of the sum of its digits at odd places and the sum of its digits at even places, is divisible by 11.

10. A number is divisible by 12 if the number is also divisible by both 3 and 4.

For Special Case

  • Divisibility of 7 – We take Unit digit & multiply with 2 then Subtract.

  • Divisibility of 13 – We take Unit digit & multiply with 4 then Add.

  • Divisibility of 17 – We take Unit digit & multiply with 5 then Subtract.

  • Divisibility of 19 – We take Unit digit & multiply with 2 then Add.


To Test Divisibility by 7, use the below rules:

1. Remove the last digit, double it, subtract it from the truncated original number and continue doing this until only one digit remains.

2. If the remaining digit is 0 or 7, or a double digit divisible by 7, then the given number is divisible by 7
Example 1: Is 112 divisible by 7?
Step I: The last digit is 2. Doube of 2 is 2*2 = 4 . 112: 11 – 2×2 = 7 (Separate the last digit & multiply with two & then subtract). The remaining digit is 7. Thus 112 is divisible by 7.

Example 2: Is 2961 divisible by 7?
Step I: 296 – 1X2 = 294
Step II : 29 – 4X2 = 21.
Here we can see 21 Is divisible by 7, then we can say 2961 is also divisible by 7.



A number is divisible by 13 if it Follows the below rules:

Example: Is 143 divisible by 13 ? Step I : 14 + 3X4 = 26 .
Here we can see 26 Is divisible by 13, then we can say 143 is also divisible by 13 .

  • A number is divisible by 17 if it Follows the below rules
  • Ex: Is 1904 divisible by 17 ? Step I : 190 – 4X5 = 170 .
    Here we can see 170 Is divisible by 17 . then we can say 1904 is also divisible by 17.


  • A number is divisible by 19 if it Follows the below rules
  • Ex. Is 149264 divisible by 19 ? Step I : 14926 + 4X2 = 14934 . Step II : 1493 + 4X2 = 1501 Step III : 150 + 1X2 = 152 Step IV : 15 + 2X2 = 19
    Here we can see 19 Is divisible by 19 . then we can say 149264 is also divisible by 19.



    Simplification
    H.C.F: It Stands for Highest Common Factor / Greatest Common Divisor (G.C.D) and Greatest Common Measure (G.C.M).
    L.C.M: It Stands for Lowest Common Factor / Lowest Common Divisor (L.C.D) and Lowest Common Measure (L.C.M).

  • The H.C.F. of two or more numbers is the greatest number that divides each one of them exactly.
  • The least number which is exactly divisible by each one of the given numbers is called their L.C.M.
  • Two numbers are said to be co-prime if their H.C.F. is 1.
  • H.C.F. of fractions = H.C.F. of numerators/L.C.M of denominators
  • L.C.M. of fractions = G.C.D. of numerators/H.C.F of denominators
  • The product of two numbers = Product of their H.C.F. and L.C.M.

  • BodmasRule: This Rule depicts the correct sequence in which the operations are to be executed, so as to find out the value of a given expression.
    Here,
    B – Bracket
    O – Of
    D – Division
    M – Multiplications
    A – Addition
    S – Subtractions

  • \((a + b)^2\) = \(a^2\) + 2ab + \(b^2\)

  • (a + b)(a – b) = (\(a^2\) – \(b^2\))

  • \((a + b)^2\) = (\(a^2\) + \(b^2\) + 2ab)

  • \((a – b)^2\) = (\(a^2\) + \(b^2\) – 2ab)

  • \((a + b + c)^2\) = \(a^2\) + \(b^2\) + \(c^2\) + 2(ab + bc + ca)

  • (\(a^3\) + \(b^3\)) = (a + b)(\(a^2\) – ab + \(b^2\))

  • (\(a^3\) – \(b^3\)) = (a – b)(\(a^2\) + ab + \(b^2\))

  • (\(a^3\) + \(b^3\) + \(c^3\) – 3abc) = (a + b + c)(\(a^2\) + \(b^2\) + \(c^2\) – ab – bc – ac)
    When a + b + c = 0, then \(a^3\) + \(b^3\) + \(c^3\) = 3abc.


  • Algebra
    Sum of first n natural numbers = \(\frac{n(n + 1)}{2}\)
    Sum of the squares of first n natural numbers = \(\frac{n(n+1)(2n+1)}{6}\)
    Sum of the cubes of first n natural numbers = \(\frac{[n(n+1)/2]}{2}\)
    Sum of first n natural odd numbers = n2
    Average = \(\frac{Sum of items}{Number of items}\)

    Arithmetic Progression (A.P)
    An A.P. is of the form a, a+d, a+2d, a+3d, …
    where a is called the ‘first term’ and d is called the ‘common difference’
    nth term of an A.P. tn = a + (n-1)d
    Sum of the first n terms of an A.P. Sn = \(\frac{n}{2[2a+(n-1)d]}\) or Sn = \(\frac{n}{2(first term + last term)}\)

    Geometrical Progression (G.P)
    A G.P. is of the form a, ar, ar2, ar3, …
    where a is called the ‘first term’ and r is called the ‘common ratio’. nth term of a G.P. tn = arn-1
    Sum of the first n terms in a G.P. Sn = a\(\frac{ \mid 1 – rn \mid}{\mid 1 – r \mid}\)


    Factorial Notation
    Let n be a positive integer. Then, factorial n, denoted n! is defined as:
    n! = n(n – 1)(n – 2) … 3.2.1.

  • Points To Remeber
  • 0! = 1.
    1! = 1.
    2! = 2.
    3! = 6.
    4! = 24.
    5! = 120.
    6! = 720.
    7! = 5040.
    8! = 40320.
    9! = 362880.

    Permutations:
    The different arrangements of a given number of things by taking some or all at a time, are called permutations.

      Examples:

    All permutations (or arrangements) made with the letters a, b, c by taking two at a time are (ab, ba, ac, ca, bc, cb).
    All permutations made with the letters a, b, c taking all at a time are: (abc, acb, bac, bca, cab, cba)

    Number of Permutations:
    all permutations of n things, taken r at a time, is given by:
    nPr = n(n – 1)(n – 2) … (n – r + 1) = \(\frac{n!}{(n – r)!}\)
    Examples:
    6P2 = (6 x 5) = 30.
    7P3 = (7 x 6 x 5) = 210.
    Cor. number of all permutations of n things, taken all at a time = n!.

  • An Important Result:
  • If there are n subjects of which p1 are alike of one kind; p2 are alike of another kind; p3 are alike of third kind and so on and pr are alike of rth kind, such that (p1 + p2 + … pr) = n.
    Then, number of permutations of these n objects is =\(\frac{n!}{(p1!).(p2)!…..(pr!)}\)
    Combinations:
    Each of the different groups or selections which can be formed by taking some or all of a number of objects is called a combination.

  • Examples:
  • Suppose we want to select two out of three boys A, B, C. Then, possible selections are AB, BC and CA. Note: AB and BA represent the same selection.
    All the combinations formed by a, b, c taking ab, bc, ca.
    The only combination that can be formed of three letters a, b, c taken all at a time is abc.
    Various groups of 2 out of four persons A, B, C, D are:
    AB, AC, AD, BC, BD, CD.
    Note that ab ba are two different permutations but they represent the same combination.
    Number of Combinations:
    The number of all combinations of n things, taken r at a time is:
    nCr = \(\frac{n!}{(r!)(n – r)!}\) =\(\frac{n(n – 1)(n – 2) … to r factors}{r!}\)

    Note:
    nCn = 1 and nC0 = 1.
    nCr = nC(n – r)

      Examples:

    1. 11C4 = \(\frac{(11 x 10 x 9 x 8)}{(4 x 3 x 2 x 1)}\) = 330
    2. 16C13 = 16C(16 – 13) = 16C3 = \(\frac{16 x 15 x 14}{3!}\)


    An experiment in which all possible outcomes are know and the exact output cannot be predicted in advance, is called a random experiment.

  • Examples:
  • Rolling an unbiased dice.
    Tossing a fair coin.
    Drawing a card from a pack of well-shuffled cards.
    Picking up a ball of a certain colour from a bag containing balls of different colours.

  • Details:
  • i.When we throw a coin, then either a Head (H) or a Tail (T) appears.
    ii.A dice is a solid cube, having 6 faces, marked 1, 2, 3, 4, 5, 6 respectively. When we throw a die, the outcome is the number that appears on its upper face.
    iii.A pack of cards has 52 cards.
    It has 13 cards of each suit, name Spades, Clubs, Hearts and Diamonds.
    Cards of spades and clubs are black cards.
    Cards of hearts and diamonds are red cards.
    There are 4 honours of each unit.
    There are Kings, Queens and Jacks. These are all called face cards.

  • Sample Space:
  • When we perform an experiment, then the set S of all possible outcomes is called the sample space.

  • Examples:
  • In tossing a coin, S = {H, T}
    If two coins are tossed, the S = {HH, HT, TH, TT}. In rolling a dice, we have, S = {1, 2, 3, 4, 5, 6}.
    Event:
    Any subset of a sample space is called an event.
    Probability of Occurrence of an Event:
    Let S be the sample and let E be an event.
    Then, \({E \subset s}\)

    P(E) =\(\frac{n(E)}{n(S)}\)
    Results on Probability:
    P(S) = 1
    0≤P(E)≤1
    P( \(\Phi\) )= 0
    For any events A and B we have : P(A ∪ B) = P(A) + P(B) – p(A ∩ B)
    If A denotes (not-A), then P(A) = 1 – P(A).

    Average
    Average : \(\frac{Sum of Observation}{Number of Observations}\)
    Suppose a Man cover a certain Distance at X kmph and an equal distance at Y kmph . Then , the average speed during the whole journey is \(\frac{2XY}{X+Y}\)

    Surds and Indices

  • Laws Of Indices :
  • 1. \(a^m \) x \(a^n\) = \(a^{ m + n }\)
    2. \(\frac{a^m}{a^n}\)= \(a^{m – n}\)
    3. \((a^m)^n\) = \(a^{mn}\)
    4. \(({ab})^n\) = \(a^n\) \(b^n\)
    5. \((\frac{a}{b})^n\) = \(\frac{a^n}{b^n}\)
    6. \((a)^0\) = 1

    Surds: Let a be rational number and n be a positive integer such that \(a^{1/n}\) = a
    Then, a is called a surd of order n.

    Laws Of Surds :
    1. a = \(a^{1/n}\)
    2. ab = a x b
    3. \(\sqrt[n]{\frac a b}\) = \(\frac {a}{b}\)
    4. \((a)^n\) = a
    5. \(\sqrt[m]{\sqrt[n]{a}}\) = \(\sqrt[mn]{a}\)
    6. \((a)^m\) = \(a^m\)


    To express x% as a fraction: We have, x% = \(\frac{x}{100}\)
    To express \(\frac{a}{b}\) as a percentage : We have, \(\frac{a}{b}\)% = (\(\frac{a}{b}\) x 100)
    If A is R% more than B, then B is less than A by, (\(\frac{R}{100+R}\) x 100)
    If A is R% less than B, then B is more than A by ,(\(\frac{R}{100-R}\) x 100)
    Population after n years : P\((\frac{1+R}{100})^n\)
    Population before n years : P\((\frac{1−R}{100})^n\)
    If the price of a commodity increases by R%, then reduction in consumption, not to increase the expenditure is : (\(\frac{R}{100+R}\) x 100)
    If the price of a commodity decreases by R%, then the increase in consumption, not to decrease the expenditure is : (\(\frac{R}{100-R}\) x 100)
    Value of Machine after n years: P\((\frac{1+R}{100})^n\)
    Value of Machine before n years :P\((\frac{1-R}{100})^n\)

    PROFIT AND LOSS
    1. Gain = Selling Price(S.P.) – Cost Price(C.P)
    2. Loss = Cost Price (C.P.) – Selling Price (S.P)
    3. Gain % = Gain x \(\frac{100}{C.P}\)
    4. Loss % = Loss x \(\frac{100}{C.P}\)
    5. S.P = \(\frac{100 + gain%}{100}\) x C.P
    6. S.P = \(\frac{100 – loss%}{100}\) x C.P
    7. C.P = \(\frac{100 – loss%}{100}\) x S.P
    8. C.P = \(\frac{100 – loss%}{100}\) x S.P
    When a person sell two similar items , one at a gain of say x% , and other at a loss of x% then the seller always incure a loss given by, Loss % = \((\frac{Common loss + gain %}{10})^2\)
    If a trader professes to sell his goods at cost price , but uses false weight , then Gain% = \((\frac{ Error }{True value–Error})\) x 100 %

    TRUE DISCOUNT
    Ex. Suppose a man has to pay Rs. 156 after 4 years and the rate of interest is 14% per annum. Clearly, Rs. 100 at 14% will amount to R. 156 in 4 years. So, the payment of Rs. now will clear off the debt of Rs. 156 due 4 years hence. We say that:
    Sum due = Rs. 156 due 4 years hence: Present Worth (P.W.) = Rs. 100;
    True Discount (T.D.) = Rs. (156 – 100) = Rs. 56 = (Sum due) – (P.W.)
    We define: T.D. = Interest on P.W.; Amount = (P.W.) + (T.D.)
    Interest is reckoned on P.W. and true discount is reckoned on the amount.
    Let rate = R% per annum and Time = T years. Then,
    P.W = \((\frac{100 * Amount}{100 * (R x T)})\) = \((\frac{100 * T.D}{(R * T)})\)
    T.D = \((\frac{(P.W.) * R x T}{100}\) = \((\frac{Amount x R x T}{100 + (R x T)}
    Sum = [latex](\frac{(S.I.) * (T.D.)}{(S.I.) – (T.D.)}\)
    (S.I.) – (T.D.) = S.I. on T.D.
    When the sum is put at compound interest, then P.W. = \((\frac{Amount}{1 + \frac {R}{100}})^T\)

    The ratio a : b represents a fraction a/b. a is called antecedent and b is called consequent. The equality of two different ratios is called proportion.
    If a : b = c : d then a, b, c, d are in proportion.
    This is represented by a : b :: c : d. In a : b = c : d, then we have a* d = b* c.
    If a/b = c/d then ( a + b ) / ( a – b ) = ( d + c ) / ( d – c ).
    TIME & WORK
    If A can do a piece of work in n days, then A’s 1 day’s work = \(\frac{1}{n}\)
    If A and B work together for n days, then (A+B)’s 1 days’s work = \(\frac{1}{n}\)
    If A is twice as good workman as B, then ratio of work done by A and B = 2:1

    Basic Formula :
    If M1 men can do W1 work in D1 days working H1 hours per day and M2 men can do W2 work in D2 days working H2 hours per day (where all men work at the same rate), then
    M1 D1 H1 / W1 = M2 D2 H2 / W2
    If A can do a piece of work in p days and B can do the same in q days, A and B together can finish it in \(\frac{pq}{(p+q)}\) days

    PIPES & CISTERNS
    If a pipe can fill a tank in x hours, then part of tank filled in one hour = \(\frac{1}{x}\)
    If a pipe can empty a full tank in y hours, then part emptied in one hour = \(\frac{1}{y}\)
    If a pipe can fill a tank in x hours, and another pipe can empty the full tank in y hours, then on opening both the pipes,
    the net part filled in 1 hour = (1/x-1/y) if y>x
    the net part emptied in 1 hour = (1/y-1/x) if x>y

    TIME & DISTANCE
    Distance = Speed X Time
    1km/hr = \(\frac{5}{8}\)m/sec
    1m/sec = \(\frac{18}{5}\)km/hr
    Suppose a man covers a certain distance at x kmph and an equal distance at y kmph. Then, the average speed during the whole journey is \(\frac{ 2xy}{(x+y)}\)km/ph.

    1.Time taken by a train x metres long in passing a signal post or a pole or a standing man is equal to the time taken by the train to cover x metres.
    2. Time taken by a train x metres long in passing a stationary object of length y metres is equal to the time taken by the train to cover x+y metres.
    3. Suppose two trains are moving in the same direction at u kmph and v kmph such that u> v, then their relative speed = u-v kmph.
    4. If two trains of length x km and y km are moving in the same direction at u kmph and v kmph, where u>v, then time taken by the faster train to cross the slower train = (x+y)/(u-v) hours.
    5. Suppose two trains are moving in opposite directions at u kmph and v kmph. Then, their relative speed = (u+v) kmph.
    6. If two trains of length x km and y km are moving in the opposite directions at u kmph and v kmph, then time taken by the trains to cross each other = (x+y)/(u+v)hours.
    7. If two trains start at the same time from two points A and B towards each other and after crossing they take a and b hours in reaching B and A respectively, then A’s speed : B’s speed = (√b : √a)
    8. Speed of Train = ( Sum of the length of two trains ) / Time taken
    9. Time taken to cross a stationary Engine = (Length of the train + Length of engine) / Speed of the train .
    10. Time taken to Cross a signal Post = Length of the train / Speed of the Train

    BOATS AND STREAM
    In water, the direction along the stream is called downstream. And, the direction against the stream is called upstream.
    If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then :
    Speed downstream = (u + v) km/hr
    Speed upstream= (u – v) km/hr
    If the speed downstream is a km/hr and the speed upstream is b km/hr, then : Speed in strill water = 1/2 (a + b) km/hr
    Rate of stream = 1/2 (a – b) km/hr

    SIMPLE AND COMPOUND INTEREST
    Let P be the principal, R be the interest rate % Per annum, and N be the time period.
    Simple Interest = \(\frac{(P * N * R)}{100 }\)
    Compound Interest = P(\(\frac{(1 + R)}{100 }\))N-P
    Amount = Principal + Interest
    Let Principal = P, Rate = R% per annum, Time = n years
    When interest is compound Annually:
    Amount = P( 1 + \(\frac{R}{100 })^n\)
    When interest is compounded Half-yearly:
    Amount = P( 1 + \(\frac{R/2}{100 })^{2n}\)
    When interest is compounded Quarterly:
    Amount = P( 1 + \(\frac{R/4}{100 })^{4n}\)
    When interest is compounded Annually but time is in fraction, say \(\frac{2}{5}\) years.
    Amount = P( 1 + \(\frac{R}{100 })^3\) x (1 + \(\frac{2}{5R}/{100})\)
    When Rates are different for different years, say R1%, R2%, R3% for 1st, 2nd and 3rd year respectively.
    Then, Amount = P[1 + \(\frac{R_{1}}{100}\)] P[1 + \(\frac{R_{2}}{100}\)] P[1 + \(\frac{R_{3}}{100}\)]
    Present worth of Rs x due n years hence is given by:
    \(\frac{x}{(1 + \frac{R}{100})^n}\)

  • Sum of the angle of a triangle is = 180 degree
  • The sum of any two side of a triangle is greater than the third side .
  • Pythagorous Theorem = Hypotenuse2 =( Base ) 2 + (Height )2
  • The line Joining the mid point of a side of a triangle to the opposite vertex is called the median .
  • In an Isoscles triangle , the altitude from the vertex bisects the base
  • The median of a triangle divide it into two triangle of the same area .
  • The area of the triangle formed by joining the mid points of the side of a given triangle is one forth of the area of the given triangle .
  • The diagonals of a parallelogram bisect each other.
  • Each diagonal of a parallelogram divides it into triangles of the same area.
  • The diagonals of a rectangle are equal and bisect each other.
  • The diagonals of a square are equal and bisect each other at right angles.
  • The diagonals of a rhombus are unequal and bisect each other at right angles.
  • A parallelogram and a rectangle on the same base and between the same parallels are equal in area.
  • Of all the parallelogram of given sides, the parallelogram which is a rectangle has the greatest area
  • Area of a rectangle = (Length x Breadth)
    Length = Length = \(\frac{Area}{Breadth}\) and Breadth = \(\frac{Area}{Length}\)
    Perimeter of a rectangle = 2 ( Length + Breadth )
    Area of a square = \((Side)^2\) = \(\frac{1}{2}\) \((diagonal)^2\)
    Area of an equilateral triangle = √3/4\((Side)^2\)
    Area of 4 walls of a room = 2 (Length + Breadth) x Height.
    Area of a triangle = \(\frac{1}{2}\) x Base x Height.
    Area of a triangle = √s(s-a)(s-b)(s-c)
    where a, b, c are the sides of the triangle and s = 1/2(a + b + c).
    Radius of incircle of an equilateral triangle of side a = \(\frac{a}{2√3}\)
    Radius of Circum-circle of an equilateral triangle of side a = \(\frac{a}{√3}\)
    Radius of incircle of a triangle of area \(\bigtriangleup\) semi-perimeter r = \(\frac{\bigtriangleup}{S}\)
    Area of parallelogram = (Base x Height).
    Area of a rhombus = \(\frac{1}{2}\)x (Product of diagonals).
    Area of a trapezium = \(\frac{1}{2}\)x (sum of parallel sides) x distance between them.
    Area of a circle = \(\Pi\)\(R^2\) where R is the radius
    Circumference of a circle = 2\(\Pi\)R
    Length of an arc =2\(\Pi\)R\(\theta\)/360, where \(\theta\) is the central angle.
    Area of a sector = \(\frac{1}{2}\)(arc x R) = \(\Pi\)\(R^2\)\(\theta\)/360
    Circumference of a semi-circle =\(\Pi\)R

    CUBOID
    Let length = l, breadth = b and height = h units.
    Then Volume = (l x b x h) cubic units.
    Surface area = 2(lb + bh + lh) sq. units.
    Diagonal = √( l2 + b2 + h2 ) units.

    CUBE
    Let each edge of a cube be of length a. Then, Volume = a3 cubic units.
    Surface area = 6a2 sq. units. Diagonal = √3a units.

    CYLINDER
    Let radius of base = r and Height (or length) = h. Then,
    Volume = \(\Pi\)2h cubic units.
    Curved surface area = 2\(\Pi\)h sq. units.
    Total surface area = 2\(\Pi\)(h + r) sq. units.

    CONE
    Let radius of base = r and Height = h. Then,
    Slant height, l = √(h2 + r2 ) units.
    Volume = \(\frac{1}{3}\)\(\Pi\)r2h cubic units.
    Curved surface area = \(\Pi\)rl sq. units.
    Total surface area = (\(\Pi\)rl + \(\Pi\)r2) sq. units.

    SPHERE
    Let the radius of the sphere be r. Then
    Volume = \(\frac{4}{3}\)\(\Pi\)r3 cubic units.
    Surface area = 4\(\Pi\)2 sq. units.

    HEMISPHERE
    Let the radius of a hemisphere be r. Then,
    Volume = \(\frac{2}{3}\)\(\Pi\)r3 cubic units.
    Curved surface area = 2\(\Pi\)2 sq. units.
    Total surface area = 3\(\Pi\)2 sq. units
    Note: 1 litre = 1000 \(cm^3\)



    Trignometry Formula
    \(cos^2\)(X) + \(sin^2\)(X) = 1
    1 + \(Tan^2\)(X) = \(Sec^2\)(X)
    1 + \(Cot^2\)(X) = \(Cosec^2\)(X)
    cos( X\(\pm\)Y ) = cos( x )cos( y )\(\pm\)sin( x )sin( y)
    sin( X\(\pm\)Y ) = Sin( x )cos( y )\(\pm\)Cos( x )sin( y)
    sin(2x) = 2 sin( x) cos( x)
    cos(2x) = 2\(Cos^2\)(x) – 1
    sin(2x) = \(Cos^2\)(x) – \(Sin^2\)(x)
    cos(2x) = 1 − 2 sin( x)
    tan( X \(\pm\) Y) = [tan( x) \(\pm\)tan( y)]/ tan( y)]/ [ 1 \(pm\)tan( x)tan( y)]
    sin( x) x sin( y) = \(\frac{1}{2}\)[cos(x−y) − cos( x+y)]
    cos( x) x cos( y) = \(\frac{1}{2}\)[cos(x−y) + cos( x+y)]
    sin( x)x cos( y) = \(\frac{1}{2}\)[sin(x+y)+ sin( x−y)]
    cos( x) x sin( y) = \(\frac{1}{2}\)[sin(x+y)− sin( x−y)]
    sinθcosecθ = 1
    \(sin^2\)θ = 1− \(cos^2\)θ
    \(Cos^2\)θ = 1− \(Sin^2\)θ

    Trignometric Values:

    Degrees 30º 45º 60º 90º 180º
    Radians 0 \(\frac{\pi}{6}\) \(\frac{\pi}{4}\) \(\frac{\pi}{3}\) \(\frac{\pi}{2}\) \(\pi\)
    sinθ 0 \(\frac{1}{2}\) \(\frac{√2}{2}\) \(\frac{√3}{2}\) 1 0
    Cosθ 1 \(\frac{√3}{2}\) \(\frac{√2}{2}\) \(\frac{1}{2}\) 0 -1
    Tanθ 0 \(\frac{1}{√3}\) = \(\frac{√3}{3}\) 1 √3 NA 0


    Parallel Lines:

    Corresponding angles are equal i.e : 1=5 , 2=6 , 4=8 , 3=7

    Alternate interior angles are equal i.e : 4=6 , 5=3

    Alterate Exterior angle are equal : 2=8 , 1=7
    In other words interior angles same side = 2 right angles = 180° = \(\pi\)radians = \(\frac{1}{2}\) turn
    Sum of exterior angles same side ∠2 + ∠7 = 180°

    Types of Angle
    Acute angle = 0° – 90°
    Right Angle = 90°
    Obtuse angle = 90° – 180°
    Straight Angle = 180°
    Reflex Angle = 180° – 360°
    Complete angle = 360°
    Complementary Angle = sum of two angles = 90°
    Supplementary angle = sum of two angles = 180°

    Triangle
    Vertices A, B, C Angles = ∠A, ∠B, ∠C
    Three sides AB, BC, AC
    Triangle of two Types:
    A. Based on sides
    Equilateral Triangle : All three sides equal
    Isosceles Triangle : Two sides equal
    Scalene Triangle : all three sides different
    B. Based on Angles
    Right Angle Triangle : One angle 90°
    Obtuse Angle Triangle : One angle more than 90°
    Acute Angle Triangle : All angles less than 90°
    When \(AC^2\) \(AB^2\) + \(BC^2\) (Obtuse angle triangle)
    When\(AC^2\) = \(AB^2\)+\(BC^2\) (Right angle triangle)

    Center Of Triangle

    A. CENTROID
    A median divides triangle into 2 equal parts AG : GD = 2:1
    BG : GB = 2:1 CG : GF = 2:1
    2 x \(Median^2\) + 2 \(( ½ the third side )^2\) = Sum of the square of other sides.
    2\(AD^2\) + 2 X \((BC/2)^2\) = \((AB)^2\) + \((AC)^2\)
    B. ORTHOCENTER
    ∠A + ∠BOC = 180 Degree = ∠C + ∠AOB = ∠B + ∠AOC
    C. Circumcenter
    ∠QCR = 2∠QPR
    D. Incenter
    ∠QIR = 90 + \(\frac{1}{2}\)∠P
    ∠QIR = 90 – \(\frac{1}{2}\)∠P if QI + RI be the angle bisector of exterior angles at Q & r.

    Chord Of A Circle
    Case – I When Intersect Internally
    PA x PB = PC x PD
    Case – II When Intersect Externally
    PA x PB = PC x PD

    Tangents:
    Case – I: In-Direct Common Tangent / Transverse Common Tangent
    AB : BC = r1 : r2
    Assume AC = Distance between centres = d
    \(PQ^2\) = RS^2 =d^2- \((r1 + r2)^2\)
    Case – II: Direct Common Tangent
    \(CD^2[latex] = [latex]AB^2 [latex] = [latex]d^2[latex] – [latex](r1 – r2)^2\)

  • The face or dial of a watch is a circle whose circumference is divided into 60 equal parts, called minute spaces.
  • A clock has two hands, the smaller one is called the hour hand or shorthand while the larger one is called the minute hand or long
    hand.
  • I. In 60 minutes, the minute hand gains 55 minutes on the hour
    hand.
    II. In every hour, both the hands coincide once.
    III. The hands are in the same straight line when they are coincident
    or opposite to each other.
    IV. When the two hands are at right angles, they are 15 minute
    spaces apart.
    V. When the hands are in opposite directions, they are 30
    minute spaces apart.
    VI. Angle traced by hour hand in 12 hrs = 360°.
    VII. Angle traced by minute hand in 60 min. = 360°.

  • Too Fast and Too Slow: If a watch or a clock indicates 8.15, when the correct time is 8, it is said to be 15 minutes too fast.
  • On the other hand, if it indicates 7.45, when the correct time is 8, it is said to be 15 minutes too slow
  • Bankers’ Discount : Suppose a merchant A buys googds worth, say Rs. 10,000 from another merchant B at a credit of say 5 months.
    Then, B prepares a bill, called the bill of exchange. A signs this bill and allows B to withdraw the amount from his bank account after exactly 5 months.

  • The date exactly after 5 months is called nominally due date. Three days (known as grace days) are added to it to get a date, known as legally due date.

  • Suppose B wants to have the money before the legally due date.
    Then he can have the money from the banker or a broker, who deducts S.I. on the face value (i.e., Rs. 10,000 in this case) for the period from the date on which the bill was discounted (i.e., paid by the banker) and the legally due date. This amount is known as Banker’s Discount (B.D.)


  • Thus, B.D. is the S.I. on the face value for the period from the date on which the bill was discounted and the legally due date

  • Banker’s Gain (B.G.) = (B.D.) – (T.D.) for the unexpired time