Question

A man can do a piece of work in 5 days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone? 6 days 6.5 days 7.5 days 7 days

Answer 1

Answer:

7.5 days

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Step-by-step explanation:

let say work = w

then 5m = w  ( men take 5 days)

3m + 3s = w    (men & son together take 3 days)

3(w/5) + 3s = w     - putting m from 1st equation into 2nd equation

3w +15s = 5w

15s = 2w

7.5s = w

so s ( son) will take 7.5 days