SSC CHSL 9 Jan 2017 Shift 3 Paper

Let total work to be done = 56 units
Pradeep has done 1/4 of a job i.e. $\frac{56}{4}=14$ units in 14 days
⇒ Pradeep's efficiency = $\frac{14}{14}=1$ unit/day
Work left = 56 - 14 = 42 units which is done by Saquib in 56 days
⇒ Saqub's efficiency = $\frac{42}{56}=0.75$ units/day
Pradeep and Saquib 1 day's work = 1 + 0.75 = 1.75 units/day
∴ Time taken by them together to complete the work = $\frac{56}{1.75}=32$ days