A can do a piece of work in 10 days. B can do it in 15 days. With the assistance of C, they completed the work in 5 days. Find how many days C alone can do it.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 30.
Given that
A can do a piece of work in 10 days.
B can do it in 15 days.
A, B, and C can complete together in 5 days
Total work = LCM (10, 15, 5) = 30
The efficiency of A = 30/10 = 3
The efficiency of B = 30/15 = 2
The combined efficiency of A, B, and C = 30/5 = 6
So, the efficiency of C = 6 - (3+ 2) = 6 - 5 = 1
Hence, C alone can complete the work in = 30/1 = 30 days