A man does a piece of work in 5 days but with the help of his son he completes the work in 3 days how long will the son take to complete it?
2007-06-12 19:18:41 · 4 answers · asked by Max 1 in Science & Mathematics ➔ Mathematics
One man does a work alone in 5 days.
Meaning he did 1/5 of the work in a day
Together with a boy, he could do it in 3 days.
Let the boy alone finish the work in x days.
So, in one day, the boy can complete 1/x of the work.
The man does 1/5 work, boy does 1/x work in 1/3 of total time:
1/5 + 1/x = 1/3
1/x = 1/3 - 1/5
1/x = 5 - 3/15
1/x = 2/15
x = 15/2
x = 7.5
The son alone can do the work in 7.5 days.
2007-06-12 20:19:31 · answer #1 · answered by Akilesh - Internet Undertaker 7 · 0⤊ 0⤋
7 and 1/2 days.
Since the work is completed in 3 days the son must be doing 2 days worth of work while the man is doing 3 days. So the son's rate of work is 2/3 of the fathers.
So if the father would take 5 days, the son will take 5/(2/3) = 5 (3/2) = 7.5 days
2007-06-12 19:26:24 · answer #2 · answered by Anonymous · 0⤊ 0⤋
amount of work = 1 man X 5 days
= 5 man days
= 3 man days + 3 son days
3 son days = 2 man days
1 son day = 2/3 man days
no of days for son = amount of work in man days/ no of man
= 5 / (2/3) = 7.5 days
2007-06-12 19:28:43 · answer #3 · answered by Karoly 2 · 0⤊ 0⤋
7.5 days
2007-06-12 19:49:34 · answer #4 · answered by Anonymous · 0⤊ 1⤋