Statistics for the Behavioral Sciences by Frederick J. Gravetter, Larry B. Wallnau ISBN 10: 1305504917 ISBN 13: 9781305504912

636 APPENDIX A | Basic Mathematics Review
3. Multiplying and Dividing Negative Numbers When the two numbers being
multiplied (or divided) have the same sign, the result is a positive number. When
the two numbers have different signs, the result is negative. For example,
3 3 (22) 5 26
24 3 (22) 5 18
The first example is easy to explain by thinking of multiplication as repeated
addition. In this case,
3 3 (22) 5 (22) 1 (22) 1 (22) 5 26
You add three negative 2s, which results in a total of negative 6. In the second
example, we are multiplying by a negative number. This amounts to repeated subtraction.
That is,
24 3 (22) 5 2(22) 2 (22) 2 (22) 2 (22)
5 2 1 2 1 2 1 2 5 8
By using the same rule for both multiplication and division, we ensure that these two
operations are compatible. For example,
which is compatible with
Also,
which is compatible with
26 4 3 5 22
3 3 (22) 5 26
8 4 (24) 5 22
24 3 (22) 5 18
LEARNING CHECK
1. Complete the following calculations:
a. 3 1 (28) 1 5 1 7 1 (21) 1 (23)
b. 5 2 (29) 1 2 2 (23) 2 (21)
c. 3 2 7 2 (221) 1 (25) 2 (29)
d. 4 2 (26) 2 3 1 11 2 14
e. 9 1 8 2 2 2 1 2 (26)
f. 9 3 (23)
g. 27 3 (24)
h. 26 3 (22) 3 (23)
i. 212 4 (23)
j. 18 4 (26)
ANSWERS
1. a. 3 b. 20 c. 21 d. 4 e. 20
f. 227 g. 28 h. 236 i. 4 j. 23