Question

40 construction workers were building a house. Each day, they were able to build $\frac{1}{60}$ of the house. How many more workers should be hired if the owner of the house wants the house to be completed in 30 days?

• A. 40
• B. 80
• C. 60
• D. 20

Answer 1

The correct option is A 40

If more workers are hired, the house can be completed in less number of days.
$\therefore$ This is a case of inverse proportion.

Let the number of days taken by 40 workers to finish the house be x.
The workers can construct $\frac{1}{60}$ of the house in a day.
Based on this infromation, we can write:
$\frac{1}{60}\times$ x = 1
$\Rightarrow$ x = 60
$\therefore$ 40 workers need 60 days to construct the house.
Using the formula for inverse proportion,
$\text{Number of workers}\times \text{Number of days}=constant$
$\Rightarrow 40\times 60=30\times \text{Number of workers required}$
$\therefore \text{Number of workers required}=\frac{40\times 60}{30}=80$
$\therefore$ 80 workers can finish the work in 30 days.
$\Rightarrow 80-40=40$ more workers are required to build the house in 30 days.