A can do a piece of work in 7 days of 9 hours each and B can do it in 6 days of 7 hours each. How long will they take to do it, working together 8 hours a day?  Answers:
A) 2 days
B) 5 days
C) 7 days
D) 3 days
E) 9 days
Sol. A can complete the work in (7 x 9) = 63 hours.   B can complete the work in (6 x 7) = 42 hours.   A’s 1 hour's work = (1/63) and B's 1 hour's work =(1/42)   (A + B)'s 1 hour's work =(1/63)+(1/42)=(5/126)   Both will finish the work in (126/5) hrs.   Number of days. of (42/5) hrs each =(126 x 5)/(5 x 42)=3 days   Ans: 3 days
<result>D</result>
A can do a piece of work in 7 days of 9 hours each and B can do it in 6 days of 7 hours each. How long will they take to do it, working together 8 hours a day?