Question

A, B and C working separately can do a piece of work in 11 days, 20 days and 55 days respectively. In how many days the work will be completed if A is assisted by B and C on alternate days? 

(a) 8 

(b) 4 

(c) 6 

(d) 2

Answer 1

Option(a) 8

Explanation:

LCM(11,20,55) = 220.  

Let total  work is 220 units such that, 

Work done by A in 1 day =  220/11 = 20  units 

 Work done by B in 1 day =  220/20 = 11  units  

Work done by C in 1 day =  220/55 = 4  units  

First day, A and B work and completes 20+11=31 units of work 

Second day, A and C work and completes 20+4=24 units of work  

So, in every 2 days, 31+24=55 units of work gets completed. in 8 days, 4×55=220 units of work gets completed.  

Therefore, ans is 8 days

Answer 2

Correct option (a) 8

Explanation:

A, B & C 2 days work = 20+20+11+4= 55