Question

If you receive an 80%, 75% , 70% and 82% in four math tests, what grade do you need to on the fifth test to average an 80% in the course.Remember to set up the linear equation and solve.

Answer 1

remember the average formula

$\bar{x}=\frac{\sum ^{\infty}_{n\mathop=0}xi}{n}$

in this case n= total number of data and xi is each of the data

to solve this problem you know that you did a total of 5 tests and have the average and you are missing one of them, it should look like this when replacing

$80=\frac{80+75+70+82+x}{5}$

clear the equation to find x, like so

$\begin{gathered} 80\cdot5=80+75+70+82+x \\ 400=80+75+70+82+x \\ x=400-80-75-70-82 \\ x=93 \end{gathered}$

You must score a 93% to obtain a 80%average on the course