Question

12 workers can build a house in 30 days. If 15 workers build the same house, how many days will they need?

• A. 24
• B. 15
• C. 37.5
• D. 48

Answer 1

The correct option is A 24

If the number of workers building the house increases, the number of days required to build the house decreases.
$\therefore$ This is a case of inverse proportion.

$Numberofworkers\times Numberofdays=constant\Rightarrow 12\times 30=15\times Numberofdays$
$\therefore Numberofdaysrequired=\frac{12\times 30}{15}=24$.