Time and work Questions1

A completes 40% of a task in 10 days and then takes the help of B and C. B is 50% as efficient as A is and C is 50% as efficient as B is. In how many more days will they complete the work? 

A) 13 1/3 

B) 8 4/7 

C) 10 2/3 

D) 9 

Sol. (B)

 A completes 40% of work in 10days. 

Given, A:B is 2:1 and B:C is 2:1 

Now A:B:C=4:2:1 A’s work 4*10(days)=40% 

Remaining 60%=60/(4+2+1)7=8 4/7 days.