**Answer:** Option D

**Explanation:**

Sum of 10 even numbers = 10 * 11 = 110

Average = \(\frac{110 }{10}\) = 11

**2. The average of 11 numbers is 10.9. If the average of first six is 10.5 and that of the last six is 11.4 the sixth number is? **

**Answer:** Option D

**Explanation:**

1 to 11 = 11 * 10.9 = 119.9

1 to 6 = 6 * 10.5 = 63

6 to 11 = 6 * 11.4 = 68.4

63 + 68.4 = 131.4 – 119.9 = 11.5

6th number = 11.5

**3. The average of first ten prime numbers which are odd is? **

**Answer:** Option D

**Explanation:**

Sum of first 10 prime no. which are odd = 158

Average = \(\frac{158 }{10}\) = 15.8

**4. The average of first 10 natural numbers is? **

**Answer:** Option B

**Explanation:**

Sum of 10 natural no. = \(\frac{110 }{2}\) = 55

Average = \(\frac{55 }{10}\) = 5.5

**5. The average of first 10 odd numbers is? **

**Answer:** Option B

**Explanation:**

Sum of 10 odd no. = 100

Average = \(\frac{100 }{10}\) = 10

**Answer:** Option C

**Explanation:**

Sum of 10 prime no. = 129

Average = \(\frac{129 }{10}\) = 12.9

**2. The average age of three boys is 15 years and their ages are in proportion 3:5:7. What is the age in years of the youngest boy? **

**Answer:** Option B

**Explanation:**

3x + 5x + 7x = 45

x =3

3x = 9

**3. The average of 1st 3 of 4 numbers is 16 and of the last 3 are 15. If the sum of the first and the last number is 13. What is the last numbers?**

**Answer:** Option C

**Explanation:**

A + B + C = 48

B + C + D = 45

A + D = 13

A – D = 3

A + D = 13

2D = 10

D = 5

**4. The average of 9 observations was 9, that of the 1st of 5 being 10 and that of the last 5 being 8. What was the 5th observation? **

**Answer:** Option A

**Explanation:**

Let t1 to 9 = 9 * 9 = 81

1 to 5 = 5 * 10 = 50

5 to 9 = 5 * 8 = 40

5th = 50 + 40 = 90 – 81 = 9

**5. The average of 10 numbers is calculated as 15. It is discovered later on that while calculating the average, one number namely 36 was wrongly read as 26. The correct average is?**

**Answer:** Option C

**Explanation:**

10 * 15 + 36 – 26 = \(\frac{160 }{10}\) = 16

**Answer:** Option D

**Explanation:**

23 + 29 + 31 + 37 + 41 = \(\frac{161 }{5}\) = 32.2

**2. The average age of 8 men increases by 2 years when two women are included in place of two men of ages 20 and 24 years. Find the average age of the women?**

**C**. 30 years

**D**. 18 years

**Answer:** Option C

**Explanation:**

20 + 24 + 8 * 2 = \(\frac{60 }{2}\) = 30

**3. A team of eight entered for a shooting competition. The best marks man scored 85 points. If he had scored 92 points, the average scores for. The team would have been 84. How many points altogether did the team score? **

**D**. 656

**Answer:** Option B

**Explanation:**

8 * 84 = 672 – 7 = 665

**4. The average age of a husband and a wife is 23 years when they were married five years ago but now the average age of the husband, wife and child is 20 years(the child was born during the interval). What is the present age of the child?**

**B**. 2 years

**C**. 3 years

**D**. 4 years

**Answer:** Option D

**Explanation:**

28 * 2 = 56

20 * 3 = 60

———–

4 years

**5. In a hostel there were 100 students. To accommodate 20 more students the average is decreased by rupees 5. But total expenditure increased by Rs.400. Find the total expenditure of the hostel now? **

**B**. Rs.4600

**C**. Rs.5400

**D**. Rs.2300

**Answer:** Option C

**Explanation:**

100x + 400 = 12(x – 5)

x = 50

100 * 50 + 400 = 5400