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A , B and C can complete a work in 2 h. If A does the job alone in 6 h and B in 5 h, how long will it take for C to finish the job alone?
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- 51/2 h
- 71/2 h
- 9 h
- 41/2 h
Correct Option: B
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
