1/30 + 1/40 = 7/120
Both can finish the work in 120/7 days
A can do a piece of work in 30 days while B can do it in 40 days. In how many days will they finish it together?
[1] 120/7
[2] 95/8
[3] 123/9
[4] 150/7
[5] None