SSC CHSL 2022 PYQ — Question 75

The correct answer is option 1 i.e. 22.5 days

Given:

Time taken by A alone = 15 days

Time taken by A and B together = 9 days

Concept Used:

Time taken by A and B together will be $\frac{1}{A + B} = \frac{1}{A} + \frac{1}{B}$    .....(i)

Explanation:

Let the time taken by B alone to complete the work be x days.

Using equation (i), we get

$\frac{1}{9} = \frac{1}{15} + \frac{1}{x}$

⇒ $\frac{1}{x} = \frac{1}{9} - \frac{1}{15}$

⇒ $\frac{1}{x} = \frac{2}{45}$

⇒ x = 45/2

⇒ x = 22.5

Hence B alone can do the work in 22.5 days.