A mason can build a tank in 12 h After working for 6 h he took the help of a boy and finished the wo...........

Quant (SSC) Time and work

A mason can build a tank in 12 h. After working for 6 h, he took the help of a boy and finished the work in another 5 h. The time that the boys will take alone to complete the work is

30 h

45 h

60 h

64 h

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Explanation:

Work done by Mason in 1 h = 1/12
Work done by Mason in 6 h = 6/12 = 1/2
∴ Remaining work = 1 – 1/2 = 1/2
Now, let the boys finish the work in x h
Then, work done by Mason and boy in 1 h
= 5 × x + 12/12x = 1/2
⇒ 5x + 60/12x = 1/2
⇒ 10x + 120 = 12x
⇒ x = 60 h.