Father is 5 times faster than son. Father completes a work in 40 days before son. If both of them work together, when will the work get complete? Choose the correct option.
A) 8 1/0  B) 8 1/3  C) 8 1/8  D) 8 1/6  E) 8 1/5
As efficiency is inversely proportional to days, If Father : son's efficiency is 5 : 1, then Days taken by them should be 1 : 5. Assume, the days taken by them are k, 5k.   Given that father takes 40 days less. So 5k - k = 40 ⇒⇒ k = 10   Father takes 10 days to complete the work. Total work is 10 x 5 = 50 units.   If both of them work together, they complete 5 + 1 units a day. 6/day. To complete 50 units, they take 50/6 = 8 1/3 days.   Ans: 8 1/3
<result>B</result>
Father is 5 times faster than son. Father completes a work in 40 days before son. If both of them work together, when will the work get complete?