SSC CHSL 10 Jan 2017 Shift 1 Paper

Let total work to be done = 200 units
Work done by A in 50 days = $\frac{75}{100}\times 200=500$ units
A's efficiency = $\frac{150}{50}=3$ units/day
Remaining work = 200 - 150 = 50 units
Let B's efficiency = x units/day
Now, A and B complete remaining work in 10 days
⇒ $\left(3+\mathit{x}\right)\times 10=50$
⇒ $3+\mathit{x}=\frac{50}{10}=5$
⇒ $\mathit{x}=5-3=2$
∴ Time taken by B to complete the whole work alone = $\frac{200}{2}=100$ days