Pre-Algebra Demystified

EXAMPLE

Multiply (þ9)ð
 5 Þ:

SOLUTION

Multiply 9 5 ¼45 and give the answer a
(negative) sign. Hence, (þ9)

ð
 5 Þ¼
45.

Math Note: Multiplication can be shown without a times sign. For

example,ð
 3 Þð
 5 Þmeansð
 3 Þð
 5 Þ. Also, a dot can be used to repre-

sent multiplication. For example, 5 3 2 means 5 3 2.

To multiply three or more non-zero integers, multiply the absolute values and

count the number of negative numbers. If there is an odd number of negative

numbers, give the answer a
sign. If there is an even number of negative signs,

give the answer aþsign.

EXAMPLE

Multiplyð
 3 Þð
 4 Þð
 2 Þ:

SOLUTION

Multiply 3 4  2 ¼24. Since there are 3 negative numbers, the answer is

negative. Hence,ð
 3 Þð
 4 Þð
 2 Þ¼
24.

EXAMPLE

Multiplyð
 5 Þ(þ3)(þ4)ð
 2 Þ:

SOLUTION

Multiply 5 3  4  2 ¼120. Since there are 2 negative numbers, the answer

is positive. Hence,ð
 5 Þ(þ3)(þ4)ð
 2 Þ¼þ120.

PRACTICE

Multiply:

1. ð
   8 Þð
   5 Þ


2. (þ6)ð
   2 Þ


3. (þ4)(þ6)


4. ð
   3 Þ(þ5)


5. ð
   4 Þ(þ7)


6. ð
   3 Þð
   4 Þ(þ2)


7. (þ3)ð
   2 Þð
   6 Þ(þ9)


8. (þ10)(þ2)ð
   6 Þ(þ9)


9. (þ8)ð
   4 Þð
   3 Þ(þ8)ð
   2 Þ(þ6)


10. ð
    3 Þ(þ10)ð
    8 Þð
    2 Þ(þ4)ð
    3 Þ

28 CHAPTER 2 Integers