A and B can together finish a work in 30 days. They worked at it for 20 days and then B let. The remaining work was done by A alone in 20 more days. B alone can do the entire work inoption
48 days
50 days
54 days
60 days
Explanation:
According to the question,
A+B`s 1-day work = 1/30.
A+B`s 20 days work = 20 $\times$ 1/30 = 2/3.
Remaining work left = 1-2/3 = 1/3.
A does 1/3 work in ---> 20 days.
A does 1 work in ---> x days.
=> x = 3 $\times$ 20 = 60 days.
A will take 60 days to complete the whole work.
So, A`s 1-day work = 1/60.
Therefore, B`s 1-day work = (A+B)`s 1-day work - A`s 1-day work.
=> 1/30 - 1/60 = 1/60
So, B`s 1-day work = 1/60
Hence, B will complete the entire work alone in 60 days.