### Home > CC3 > Chapter 1 > Lesson 1.1.3 > Problem1-21

1-21.

Latisha’s friend Brandee forgot to make up a test and had these scores: $80\%$, $92\%$, $91\%$, $75\%$, $89\%$, $84\%$, $0\%$, and $85\%$.

1. Calculate Brandee’s mean. (Refer to the glossary if you do not remember how to do this.) Does this mean score really represent her abilities? Why or why not?

The mean is the sum of all the scores divided by the number of scores.

Compare this number with her scores. Does it seem right? Why or why not?

$\frac{80+92+91+75+89+84+0+85}{8}=74.5\%$

2. Brandee persuaded her teacher, Ms. Juarez, to allow her to make up the missed test. Brandee received a $78\%$. Calculate her new mean.

See part (a) for the definition of mean.

$\frac{80+92+91+75+89+84+78+85}{8}=84.25\%$

3. What difference did the $0\%$ score make? Does this new mean represent Brandee’s ability more accurately?

How did a $78\%$ instead of a $0\%$ change her average? Does it seem like the new average is better? How?