On your first four math tests you earned a 85, 80, 95, and a 65 (hey, anyone can have a bad day). What must you earn on your next test to have a mean score of at least 80?
To find the answer, first we'll set up an equation to find the mean of the 5 tests (after you take the next test there will be 5 of them). Let's call that final test x.
Now let's solve for x. We'll start by adding the scores on top:
Next, multiply 80 by 5.
Finally, subtract 325 from 400.
You must earn at least a 75 on the next test to have a B average.