Problem: Abir can do a piece of work in 80 days. He works for 10 days and then Bashir alone finishes the rest of the work in 42 days. How much time would it take for the two of them together to complete the whole work?

View all: BANGLADESH BANK | ASSISTANT DIRECTOR | WRITTEN QUESTION SOLVE(MATH) | 2005

Correct Answer:  30 days required for the two of them together to complete the whole work.

Explanation:

In 80 days. Abir can do 1 portion of workIn 10 days.

Abir can do $\frac{1 x 10}{80}$ portion of work

The rest of the work = 1 —$\frac{1 }{8}$ = $\frac{7}{8}$ portion.

Now Bashir takes 42 days to complete = $\frac{7}{8}$ portion of the work

Now Bashir takes 1 days to complete = $\frac{7}{8×42}$ portion of the work= $\frac{1}{48}$ portion of the work

In 1 day Abir & Bashir together can do = $\frac{1}{80}+\frac{1}{48}$ portion= $\frac{1}{30}$ portion

$\frac{1}{30}$ portion of the work they can do in = 1 day

1 portion of the work they can do in = 1 x 30 = 30 day

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