Box Plots, Averages, Etc

Question

Your science teacher recently gave a quiz to 28 students present in class. The class average was an 82.5. Five students that were absent made up the quiz after school and their scores were a 78, 89,92,,99, & 63. Find the new class average with the new scores

Answer 1

Take the average for the 28 students, which is 82.5, and multiply that by 28. Then add in the five new scores. Take your total and divide by 33, which is the number of student who took the quiz in the first place plus the five new ones. That is your new average.

Answer 2

The formula for an average is: (sum of values) / (count of values)

The problem gives, for 28 students,

(Ave for 28 students) = (sum of 28 values) / 28

therefore,

(sum of 28 values) = 28*(ave for 28 students)

(sum of 28 values) = 28*82.5

For 33 students, average is:

( ( sum of 28 values ) + 78 + 89 +92 + 99 + 63) ) / (28+5)

(28*82.5 + 78 + 89 +92 + 99 + 63) ) / (28+5)

82.76