Question

3. A can do a piece of work in 80 days. He works at it for 10 days and then B alone finishes the work in 42 days. In how many days A and B together can do it?*
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Answer 1

Answer:

30 days

Step-by-step explanation:

Now, A can do a piece of work in 80 days. So, let the TOTAL WORK = 80 units.

A -> 80 days = 1 unit/day

So, in 10 days, A has completed 10 units.

Remaining Work = 70 units.

Now, B finishes this in 42 days. So rate of work if B = 7042  = 53 unit/day

Thus, A + B = 1+53  =  83  

So, TIME TAKEN =  8083  = 30 Days (Answer)