Question

Amy earned an 85% on her math test. She got 3 questions wrong. How many question were on the test? Explain your thinking.

Answer 1

21

Explanation:

85% is the same as the fraction
`(85)/(100)`, so in order to figure this problem out, you would set that proportional to 3/x. This is going to tell you how many are right.

`(85)/(100) =(3)/(x)`

Now you are going to cross multiply which means you will multiply 85 and x and 3 and 100 so it will look like this:

85x=300

Now you are going to divide by 85 on both sides of the equation to get x by itself. 300/85 = 3.5 and 85x/85 = x which means that x=3.5, but you are not done yet.

The next step is to plug x in so it will look like 3/3.5 since we want to get three wrong we are going to multiply the numerator and denominator by 6 to get 18/21 which is 3 questions wrong.