SSC CGL 2016 PYQ — Question 13

The correct answer is option 4 i.e. $3 \frac{8}{11}$ hours.

John can do $\frac 1 2$ work in 3 hours so that he can complete the entire work in 6 hours.
Remaining work = 1 - 1/2 = 1/2

Joe does 1/4 of the remaining work i.e 1/8 work in 1 hour , So he can complete the entire work in 8 hours.

Now remaining work = 3/8

George finishes the remaining work in 5 hour.

George do 3/8 work in 5 hours ,So he can complete entire work in 40/3 hours.

If all three work together, then,

$\frac 1 6 + \frac 1 8 + \frac 3{40 }$ = 120/44 = 30/11

So, the answer would be option d) $2 \frac{8}{11}$ hours