Question

You spend $11 on school supplies. You purchase pencils for $0.25 each and pens for $2 each. You purchase a total of 30 pencils and pens. How many of each did you purchase?

Answer 1

You bought 28 pencils and 2 pens.

Explanation:

Define the following variables

X: Number of pencils bought

Y: Number of pens bought

Following the problem statement we have

X + Y = 30 we bought 30 pencils and pens (1)

0.25X +2Y = 11 Total cost of purchases (2)

We may solve this system using substitution. In Eq 1

Y = 30 -X (3)

Replacing (3) in (2)

0.25X +2(30-X) = 11

0.25 X + 60 -2X =11

60-11 = 2X-0.25X

49 = 1.75 X

X = 28 Pencils (4)

(4) in (3)

Y = 30 - 28 = 2