Mrs. Vogel is buying packs of gum for her students. It costs $7 for a 3 packs but she needs to buy 21 packs. How much will she spend on 21 packs of gum?

Question

Mrs. Vogel is buying packs of gum for her students. It costs $7 for a 3 packs but she needs to buy 21 packs. How much will she spend on 21 packs of gum?

Answer 1

The answer is $49.

You can set up a ratio by putting $7 over 3 because 3 packs costs $7. Put that equal to x over 21 because we know she needs 21 packs but we don't yet know the price. Let x represent that price we need to find. Once your ration is properly set up, you can cross multiply and end up with 147 = 3x. Divide by 3 on both sides and you will end up with x = 49.

7/3 = x/21 - cross multiply

147 = 3x - divide by 3 on both sides

49 = x - 21 packs will cost Mrs. Vogel $49