Correct Answer: 71/2 h
Explanation:
Let C alone can finish the job in T hours.
According to the question,
Work done by A, B and C in 1h = 1/2
⇒ 1/6 +1/5 + 1/T = 1/2
⇒ 1/T = 1/2 - 1/6- 1/5 = (15 - 5- 6)/30
⇒ 1/T = 4/30 = 2/15
∴ T = 71/2 h
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