Question

pedro has scores of 88,80.83 and 74 after four tests. what score must he make on his fifth test to have an average of 76 or greater?

Answer 1

We start to solve this by looking for the formula that let us calculate an average value, this formula would be:

$save=\frac{1+s2+s3+s4+s5}{5}$

where Save is the average score and s is the score of each exam, Since we know the value of the score Save and 4 of the exams we can replace them in the formula, like this:

And we can solve for s5, which is the score that we need to find, like this:

$\begin{gathered} 74\times5=\frac{88+80+83+74+s5}{5}\times5 \\ 74\times5=88+80+83+s5 \\ 74\times5-88-80-83-74=88+80+83+74-88-80-83-74+s5 \\ 74\times5-88-80-83-74=s5 \\ s5=74\times5-88-80-83-74=55 \end{gathered}$

Then, Pedro must have a 55 score on the fifth test