A can do piece of work in 30 days while B can do it in 40 days. In how many days can A and B working together do it ?
70 days
42 ¾ days
27 1/7 days
17 1/7 days
Explanation:
A's one day's work = 1/30 B's one day's work = 1/40 (A + B)'s one day's work = 1/30+1/40=7/120 A and B together will take 120/7 days=17 $\dfrac{1}{7}$ days
A's one day's work = 1/30 B's one day's work = 1/40 (A + B)'s one day's work = 1/30+1/40=7/120 A and B together will take 120/7 days=17 $\dfrac{1}{7}$ days