Question

12.h.02c. wednesday weekly bell work-september 3rd
jane has the following grades on her first four math tests: 88, 92, 86, 84
in order to have a mean of 90, what does jane need to make on her fifth math test?
90
95
98
100

Explanation:

Step1: Recall mean formula

The mean $\bar{x}=\frac{\sum_{i = 1}^{n}x_{i}}{n}$, where $n$ is the number of data - points and $\sum_{i = 1}^{n}x_{i}$ is the sum of the data - points. Here, $n = 5$ and we want $\bar{x}=90$. Let the score on the fifth test be $x$. The sum of the first four scores is $88 + 92+86 + 84$.

Step2: Calculate sum of first four scores

$88+92 + 86+84=(88 + 92)+(86 + 84)=180+170 = 350$.

Step3: Set up equation for mean

We know that $90=\frac{350 + x}{5}$. Cross - multiply to get $90\times5=350 + x$.

Step4: Solve for $x$

$450=350 + x$. Subtract 350 from both sides: $x=450 - 350=100$.

Answer:

D. 100