A city has 3 new houses for every 8 old houses. If there are 18 new houses in the city, how many old houses are there? Also are you supposed to use a proportion to solve it?

Question

jacobchaotic · Answer

The ratio for this problem would be 3:8. For every three new houses, there are eight old houses. Therefore, you can make the following chart.

3 New Houses:8 Old Houses
6 New Houses:16 Old Houses
9 New Houses:24 Old Houses
12  New Houses:32 Old Houses
15 New Houses:40 Old Houses
18 New Houses:48 Old Houses
21 New Houses:56 Old Houses
24 New Houses:64 Old Houses
27 New Houses:72 Old Houses
30  New Houses:80  Old Houses
33  New Houses:88  Old Houses
36 New Houses:96  Old Houses

Basically, you add three each time to the left, and eight each time to the right. For every three houses you add, you MUST add eight to the right side.

anonymous · Answer

Thank you. So you find the unit rate and then you add to the sides until you get what you need.