Question

If five men can build a house in 21 days, how long will it take seven men to build the house, assuming all men work at the same rate?

Answer 1

This problem can be solved by inverse variations. If 5 men take 21 days, 7 men will take:

5           7

21          ?

In this case we have to equate the following:

5 * 21 = 7 * ?

= 5 * 21 / 7

= 15 days.

Answer 2

Seven men would take 15 days to build the house.

Provided that if alll men work at the same rate, work done in completing a task by more number of men would take lesser days as compared to the one where fewer number of men are assigned.

Given that 5 men can build a house in 21 days.

So, from unitary method, or simply, 1 man would take (21 × 5) days = 105 days.

Therefore 7 men would take (105/7) = 15 days.