Question

There are 7 boxes stacked on the floor in the math department supply closet. Each box has a height of 10 inches or 8 inches. The height of the stack of 7 boxes is 5 feet. How many boxes in the stack are 8 inches in height?

Answer 1

5 of the 7 boxes are 8 inches in height

Explanation:

Mathematically;

1 ft = 12 inches

So, 5 ft will measure 5 * 12 = 60 inches

So from what we have ,

We want to combine 8 and 10 inches to give 60 inches total

Let the number of 10 inches be x and the number of 8 inches be y

Mathematically;

x + y = 7 •••••(i)

10x + 8y = 60 ••••(ii)

From equation i, x = 7-y

Put this in equation ii

10(7-y) + 8y = 60

70-10y + 8y = 60

70-60 = 10y-8y

2y = 10

y = 10/2

y = 5