A and B can do a piece of work in 18 and 9 days respectively. A does the work for a few days and left, then B continued for 6 days. How many days did A and B work together ?
5 days
8 days
3
days
2 days
Explanation:
According to the question,
A`s 1-day work = 1/18
B`s 1-day work = 1/9
(A+B)`s 1-day work = 1/18 + 1/9 = 3/18. [1 work in 18/3 = 6 days]
B continued for 6 days,
So, B`s 6 days work = 6/9
Total work done by A + B together = (1-6/9) = 3/9
Hence, A+B do 3/18 work in 1day (from above)
1 work in 18/3 day = 6 day
So,3/9 work in (6 $\times$ 3/9) = 2 days
So, both A and B worked for 2 days.