Question

If 3 sacks of concrete will make 12 square feet of sidewalk, predict how many sacks of concrete are needed to make 40 square feet of sidewalk.

• A. 40
• B. 30
• C. 20
• D. 10

Answer 1

The correct option is D

10

Let the number of sacks which is needed be n.
Then, $\frac{3}{12}$ = $\frac{n}{40}$
So, 12 n = 3 $\times$ 40
On dividing both the sides by 12, we get:
$\frac{12n}{12}$ = 3 $\times$ $\frac{40}{12}$
n = $\frac{40}{4}$ = 10 sacks