SSC CHSL 11 Jan 2017 Shift 2 Paper

Let total work to be done = 50 units
Mehdi's efficiency = $\frac{50}{25}=2$ units/hr
Jahnavi is 50% more efficient than Mehdi, ⇒ Jahnavi's efficiency = $\frac{150}{100}\times 2=3$ units/hr
⇒ Mehdi and Jahanavi 1 day's work = 2 + 3 = 5 units/hr
∴ Time taken by them to finish the work together = $\frac{50}{5}=10$ hours