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?

One Comment to “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?”

1. Explain 1:

   Man completes total work in 5 days, he will do one-fifth of work in a day and along with son will do one-third of work in a day. So son alone can complete the work in 7.5 days as explained below

   Work is done by man in a day: 1/5

   Work is done by man + son in a day: 1/3

   Work is done by son in a day: 1/3 – 1/5 = 2/15

   Time take by son to complete work: 15/2 or 7.5 days

   Explain 2:

   Suppose the total work is 15, (As per the Question)

   Man does it in 5 days, then per day work =15/5=3

   With his sons per day work =15/3= 5

   Extra work = 5–3= 2

   His sons do 2 unit work per day so they would do 15 units in 15/2 days = 7.5 days

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