Question

If you can buy 1⁄4 pizza for 5 dollars, how much can you purchase for 8 dollars? Write your answer as a fraction.

Answer 1

This is a problem using proportions.

a/b = c/d where: ad = bc

1/4 : 5 = x : 8

a = 1/4 ; b = 5 ; c = x ; d = 8

get the cross products: ad = bc

1/4 * 8 = 5 * x
8/4 = 5x
2 = 5x
2/5 = x

2/5 of a pizza can be purchased for 8 dollars.

to check:

1/4 : 5 = 2/5 : 8

1/4 * 8 = 5 * 2/5
8/4      = 10/5
  2       = 2