Question

If you can buy 15 bags of potatoes for $20, then how many can you buy with $4?

Answer 1

Explanation:

15 bags for $20 can be represented with 15/20
so x bags for $4 can be represented with x/4

now if you proportion it out (ricochet), 4x15 is 60, 60 divided by 20 is 3, so you can buy 3 bags of potatoes with $4.

OR

you could do 15/20 is 0.75

0.75 times 4 is 3, so $4 can buy you 3 bags.

Answer 2

Explanation:

Remark

This is a proportion problem. It assumes that if you know 3 of the four parts of a 2 ratio proportion, you can solve for the 4th one.

Givens

number of bags = 15

Cost = 20

Different cost = 4

number of bags = ?

Formula

Number of bags / Cost = different number of bags/ New Cost

Solution

15/20 = x / 4 Multiply both sides by 4

15*4/20 = x / 4 * 4

60/20 = x

Answer x = 3

That is 4 dollars gets you 3 bags of potatoes