Question 77

A, B and C can finish a job working alone in 20, 30 and 60 days respectively. They all work together for 1 day, then A and B quit. How many days C working alone will take to finish the remaining part of the job?

Solution

Let total work = LCM of 20, 30 & 60 = 60 units

Efficiency of A = 60/20 = 3

Efficiency of B = 60/30 = 2

Efficiency of C =60/60 = 1

In 1 day they can complete (3+2+1)=6 units of work

Remaining work = 60 - 6 = 54

C alone can complete the work in 54/1 = 54 days

So the answer is option B.

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