A can do a piece of work in 7 days of 9 hours each and B alone can do it

Ans 3 Days
A's 1 hr. work=1/(7*9)=1/63
B's 1 hr. work=1/(6*7)=1/42
(A+B)'s 1 hr. work=1/63 + 1/42=105/2646
(A+B)'s 8 2/5(=42/5) hr. or 1 day work=(42/5)*(105/2646)=21/63=1/3
Therefore days to complete the work by A & B together=3
12 years agoHelpfull: Yes(18) No(1)
A: 7*9 =63
B: 6+7=42
A+B= 1/63 + 1/42 = 5/126
8 2/5 ->42/5
IE,... 126/5*5/42 = ANS:3 DAYS
12 years agoHelpfull: Yes(2) No(0)
A=7*9=63 hour
B=6*7=42 hour
so A+B=AB/(A+B)
=63*42/63+42=126/5 hour
now they will take 5/42*126/5=3 days ans
10 years agoHelpfull: Yes(1) No(0)
3 days will be the answer.. we calculated the combined work of a and b and then we have converted that in days..
10 years agoHelpfull: Yes(0) No(0)
[A + B]*8 2/5
[1/(7*9) + 1/(6*7)]*42/5
1/7[1/9 + 1/6]*42/5
[5/18]*6/5====1/3 ==3days
9 years agoHelpfull: Yes(0) No(0)
the answer is 3 days
5 years agoHelpfull: Yes(0) No(0)

A can do a piece of work in 7 days of 9 hours each and B alone can do it in 6 days of 7 hours each.how long will they take it to do working together
8 2/5 hours a day?