Tiara earns $33 washing 3 cars. At this rate, how much does Tiara earn washing 9 cars?

Step-by-step explanation:

The best way to solve this is to use a proportion. However, since this is a rate, we could also find the unit rate and multiply it by the number of cars Tiara is washing.

3x = 33 x 9

3x = 297

Now, we simply divide by 3 to get $99.

We can check this by substituting the value of x in the original proportion.

3(99) = 33 x 9

297 = 297 ✅

The other way to solve this is to divide the whole expression by the number of cars to find the unit rate. In other words, how much money does she get for washing 1 car. We can then multiply this by the number of cars to get the answer.

$33/3 for 3/3 cars

$11 for 1 car

Now, we will multiply by the number of cars she washes in this question, which is 9

$11 x 9 = 99 for 1 x 9 cars

$99 for 9 cars

Again, we have the correct answer, which we have already verified by the process above. As you can see, both methods work. However, the top method is easier and since it uses algebra, is  almost foolproof, so long as the algebraic processess are followed.