A can do a work in 45 days and B can complete the same work in 36 days. In how many days the work will be completed if both work together?
Answer: D
A completes the work in 45 days. A's one day work will be 1/45 of the work.
B's one day work will be 1/36 of the work.
Both work together, in one day, 1/45 + 1/36 of the work will get over.
In one day 81/1620 of the work will get over.
Which means the work will get over in 1620/81 days. The work will get completed in 20 days.