A can do a piece of work in 24 days. When he had worked for 4 days, B joined him. If the work was finished in 16 days, B can alone finish that work is -

Question: A can do a piece of work in 24 days. When he had worked for 4 days, B joined him. If the work was finished in 16 days, B can alone finish that work is -

Solution:
A's 1 day's work = 1/24 part
A's 16 day's work = 16/24 part
= 2/3 part

Remaining work = 1 - 2/3 = 1/3 part

1/3 part work done by B in 16 - 4 = 12 days
1 part work done by B in 12 × 3 = 36 days