Q) A builder appoints three construction workers Akash, Sunil and Rakesh on one of his sites. They take 20, 30 and 60 days respectively to do a piece of work. How many days will it take Akash to complete the entire work if he is assisted by Sunil and Rakesh every third day?

a) 10 days              b) 15 days             c) 25 days                d) 30 days

Ans:

Akash’s 1 day work = 1/20

Sunil’s 1 day work = 1/30

Rakesh’ 1 day work = 1/60

∴ (A + S + R)’s 1 day’s work = 1/20 + 1/30 + 1/60 = 6/60 = 1/10

∴ work done in 1st 3 days

= 1st day’s work + 2nd day’s work + 3rd day’s work

= 1/20 + 1/20 + 1/10 = 4/20 = 1/5

Since Time taken by A to do 1/5 work = 3 days

∴ time taken by A to do full work = 3 / (1/5) = 15 days

Hence, Answer is [B]

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