Question

A can do a certain work in the same time in which B and C together can do it. If A and B together could do it in 10 days and C alone in 50 days, then B alone could do the work in: 

(a) 15 days 

(b) 20 days 

(c) 25 days 

(d) 30 days

Answer 1

Correct option (c) 25 days

Explanation: 

First line clearly states that efficiency of A should be equal to combined efficiency of B and C.(A take same time as B and C together) 

Total Efficiency = 6

efficiency of C = 1 unit/day 

efficiency of A+B=5 unit/day

so, what should be efficiency of B so that 

A’s efficiency becomes equal to B and C’s efficiency.