Question

At the math store, one circle costs one amount, and each square costs another amount. 5 circles plus one square is 20 cents. How much would 12 circles plus 5 squares cost?

Answer 1

Answer: 61 cents

Explanation:

Let’s assume a circle is X and a square is Y.

The problem states:

5x + 1y = 20

2x + 3y = 21

Taking the 1st equation we can see that

1y = 20-5x which is the same as

y = 20–5x

If we replace y in the 2nd equation with the above we get:

2x + 3(20–5x) = 21

which is the same as

2x + 60 - 15x = 21

we can rearrange to get

2x -15x = 21 -60

which is the same as:

-13x = -39

therefore x = -39/-13 or

x = 3

We can then calculate y

If y = 20–5x, then y = 20 -15

There y = 5

So to answer you question, 12 circles plus 5 squares =

12x + 5y = 12(3) + 5(5) = 36 + 25 = 61 cents

hope this helps