A and B together finish work in 10 days. B and C in 12 days. A and C in 15 days. How many days will C take to do the work alone?
Show answer & explanation
Correct answer: A
Explanation
1-day work efficiency of A + B = 1/10
1-day work efficiency of B + C = 1/12
1-day work efficiency of A + C = 1/15
Sum of the three equations,
= 1/10 + 1/12 + 1/15
= (6 + 5 + 4)/60
= 15/60
= 1/4
1-day work efficiency of A + B + C = 1/8
1-day work efficiency of C = (A + B + C) − (A + B)
= 1/8 − 1/10
= (5 − 4)/40
= 1/40
Therefore, C alone will complete the work in 40 days.