Answer to Question #263933 in Statistics and Probability for Matheca

Question

3. In MMW class, a student’s quiz scores are 89, 92, 82, and 77. What score does the student need on the fifth quiz 

to have a mean quiz score of 85? All the quizzes have equal weights. Round your answer to the nearest whole 

number.

Answer 1

Quiz scove is 89%, 92%, 82% and 77%

We want to find scove of $5^t$ quiz so that the mean scove= 85%

Assume that fifth quiz have scove X

$Mean= \frac{Sum \; of \; all \; quiz \; scoves }{Number \; of\; quizes} \\ 0.85=\frac{0.89 + 0.92 + 0.82 + 0.77 + X}{5} \\ 0.85=\frac{3.4 +X}{5} \\ 4.25=3.4 +X \\ X=4.25 -3.4 \\ X=0.85 \\ X=85\; \%$