Question

To pass a course with a B grade a student must have an average of 80 or greater. students grades on three test are 77, 88 and 74. Find what score the student must get on the next test to get a B average or better.

Answer 1

Let x be the grade of the last test, then the average would be:

$\frac{77+88+74+x}{4}=\frac{x+239}{4}$

This has to be at least 80, then we have:

$\begin{gathered} \frac{x+239}{4}=80 \\ x+239=320 \\ x=320-239 \\ x=81 \end{gathered}$

Therefore the last test has to have a score of at least 81 to get a B.