Question

A can do a piece of work in 12 hours ,B and C can do it in 3 hours whereas A and C can do it in 6 hours.how long will B alone take to do the same work​

Answer 1

Answer:

correct answer is 4 hrs. I hope that it helps you.

Answer 2

B alone will take to do the same work​ in 4 hours.

Let the total work done be LCM of (12,3,6) = 12 units.

Given A can do the work in 12 hours.

So, work per hour done by A = 12/12 = 1 unit.

Given, A and C together can do the work in 6 hours.

So, work per hour done by both A and C = 12/6 = 2 units.

So, C alone can complete (2-1) units = 1 unit of work per hour.

Given, B and C together can do the work in 3 hours.

So, work per hour done by both B and C = 12/3 = 4 units.

So, B alone can complete (4-1) units = 3 unit of work per hour.

3 units of work B does in 1 hour.

From unitary method, 1 unit of work is done by B in (1/3) hours.

Similarly, 12 units (required) work is done by B in (12/3) = 4 hours.

So, B takes 4 hours.