Question

If 30 men can build a wall 56 meters long in 5 days, what length of a similar wall can be built by 40 men in 3 days?

Answer 1

Solution: Let x be the required length of the wall.

More men means more work will be done. (Therefore, Amount of work is directly proportional to Number of men)

Less days means less length built. (Therefore, number of days of work is directly proportional to length of wall built)

Men: 30   40  : 56 meters

Days: 5     3    : x meters

Therefore, we have:

$\frac{30}{40} \times \frac{5}{3} =\frac{56}{x}$

$30 \times 5 \times x=56 \times 40 \times 3$

$150 \times x=6720$

$x=\frac{6720}{150}$

$x=44.8$

Hence the length of wall that can be built by 40 men in 3 days is 44.8 meters