Question

Difference between work efficiencies of two friends A and B is 80%, A being more hard worker. If B takes 56 days to complete a work, find out in how many days both working together can finish the work.
1. 25 days
2. 20 days
3. 30 days
4. 14 days
5. 35 days

Answer 1

Correct Answer - Option 2 : 20 days

Given:

Efficiency of A is 80% more than B and B can finish a work in 56 days.

Concept:

This is a typical problem of time & work.

Time required to complete a work is inversely proportional to the efficiency of the worker.

Formula used:

Time required = Total work / Rate of work done

Calculations:

Efficiency of A is 80% more than B.

So, ratio of rate of work done between A and B = 180 : 100 = 9 : 5

Let’s assume, A works 9x work per day and B works 5x work per day.

Total volume of the given work = 56 × 5x = 280x

If they work together, rate of work = (9x + 5x)/day = 14x works/day

Time required = 280x/14x = 20 days