B

Let the required number of days = x days
So, 150x - (20 - x)30 = 2820
x = 19 days

D

Ramesh alone finished [latex]\frac {1}{2}[/latex] of the work in 10 days.
Remaining [latex]\frac {1}{2}[/latex] was finished by Ramesh and Dinesh together in 2 days.
Therefore, they both together can finish the complete job in 4 days.

B

Ramu takes 25 days to complete work.
Raju = 50 days Venu = 100 days
Now 70% work is left
They can complete whole work in = [latex]\frac {1}{\frac{1}{25}} + \frac {1}{50} + \frac {1}{100}[/latex]
[latex]\frac {100}{7}[/latex] days then 70% in 10 days

C

Total days Mohan worked = 3 + 3 = 6
[latex]\frac {6}{15} = \frac {2}{5}[/latex]
So [latex]\frac {3}{5} = \frac {3}{x}[/latex]
x = 5

C

Arun, Bipasha and rahul’s 1 day work = [latex]\frac {1}{10} + \frac {1}{50} + \frac {6}{50} = \frac {3}{25}[/latex]
Arun’s 1 day work = Bipasha + Rahul ‘s 1 day work
2 × ( Arun’s 1 day work) = [latex]\frac {3}{25}[/latex]
Arun’s 1 day work = [latex]\frac {3}{50}[/latex]
Bipasha’s 1 day work = [latex]\frac {1}{10} - \frac {3}{50} = \frac {2}{50} = \frac {1}{25}[/latex]