Question

susan has scored 98, 76, and 94 on her previous three tests. what score does she need on her next test so that her average (mean) is 83?

Explanation:

Step1: Calculate the total score needed

The formula for the mean (average) is $\text{Mean}=\frac{\text{Sum of values}}{\text{Number of values}}$.
If the mean of \(4\) tests (three previous + one next) is \(83\), then the sum of the four - test scores \(S = 83\times4\).

$$S=83\times4 = 332$$

Step2: Calculate the sum of the previous three scores

The sum of the previous three scores \(s=98 + 76+94\).

$$s=98 + 76+94=(98 + 76)+94=174 + 94=268$$

Step3: Calculate the score needed on the next test

Let \(x\) be the score on the next test. We know that \(S=s + x\).
So \(x=S - s\).
Substitute \(S = 332\) and \(s = 268\) into the equation:

$$x=332-268 = 64$$

Answer:

\(64\)