Two teachers A and B can complete an academic work in 10 days and 15 days respectively. They started the work together, but A left after 5 days and another teacher C joined, who alone can complete the work in 60 days. In how many days the work got completed?
A.5
B.2
C.7✓ Correct
D.6
Explanation
Total work = LCM(10,15,60)=60. A's efficiency=6, B's efficiency=4, C's efficiency=1. (A+B) work for 5 days = 10×5=50. Remaining work=10, done by (B+C) at rate 5 per day = 10/5=2 days. Total = 5+2=7 days.
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