A man can do a piece of work in 5days, but with the help of his son, he can finish it in 3days. In what time can the son do it alone? Answers:
A) 5 B) 5 1/2 C) 7 1/2 D) 6 E) 9 1/2
Son's 1day work = 1/3 - 1/5 = 2/15   Son alone can do the work in 15/2days = 7 1/2 days   Answer is 7 1/2
<result>C</result>
A man can do a piece of work in 5days, but with the help of his son, he can finish it in 3days. In what time can the son do it alone?