Page 91 - Basic College Mathematics with Early Integers

68 C HAPTE R 1 I THE WHOLE NUMBERS

Objective Finding Averages

A special application of division (and addition) is finding the average of a list of
numbers. The average of a list of numbers is the sum of the numbers divided by the
number of numbers.

sum of numbers
average =
number of numbers

PRACTICE 12 Example 12 Averaging Scores
To compute a safe time to wait A mathematics instructor is checking a simple program she wrote for averaging
for reactions to occur after the scores of her students. To do so, she averages a student’s scores of 75, 96, 81,
allergy shots are administered, and 88 by hand. Find this average score.
a lab technician is given a list
of elapsed times between Solution: To find the average score, we find the sum of the student’s scores and
administered shots and reactions. divide by 4, the number of scores.
Find the average of the times 4 75 85
minutes, 7 minutes, 35 minutes, 96 4340
16 minutes, 9 minutes, 3 minutes, 340 – 32
and 52 minutes. 81 average= = 85 20
+88 4
– 20
340 sum
0
The average score is 85.
Work Practice 12

Calculator Explorations Dividing Numbers

To divide numbers on a calculator, find the keys marked Use a calculator to divide.
, and = or ENTER . For example, to find 1. 848 , 16 2. 564 , 12
435 , 5 on a calculator, press the keys 435 , 5 3. 955890 4. 271053

= or ENTER . The display will read 87 . Thus, 32,886 143,088
5. 6.
435 , 5 = 87. 126 264
7. 0 , 315 8. 315 , 0

Copyright 2012 Pearson Education, Inc.

Answer
12. 18 minutes