A man can do a piece of work in 5days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone? Choose the correct choice from the following answers:
A) 13/2
B) 7
C) 15/2
D) 8
E) 9
Son's 1day's work = (1/3)-(1/5) = 2/5   The son alone can do the work in 15/2 days   Answer is 15/2
<result>C</result>
A man can do a piece of work in 5days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone?