- Multiplication of Signed Numbers
- Division of Signed Numbers
- Calculators
Inside Collection (Textbook): Fundamentals of Mathematics
Summary: This module is from Fundamentals of Mathematics by Denny Burzynski and Wade Ellis, Jr. This module discusses how to multiply and divide signed numbers. By the end of the module students should be able to multiply and divide signed numbers and be able to multiply and divide signed numbers using a calculator.
Let us consider first, the product of two positive numbers. Multiply:
This suggests1 that
More briefly,
Now consider the product of a positive number and a negative number. Multiply:
This suggests that
More briefly,
By the commutative property of multiplication, we get
More briefly,
The sign of the product of two negative numbers can be suggested after observing the following illustration.
Multiply -2 by, respectively, 4, 3, 2, 1, 0, -1, -2, -3, -4.

We have the following rules for multiplying signed numbers.
Multiplying signed numbers:
Find the following products.
Since the numbers have the same sign, the product is positive.
Thus,
Since the numbers have the same sign, the product is positive.
Thus,
Since the numbers have opposite signs, the product is negative.
Thus,
Since the numbers have opposite signs, the product is negative.
Thus,
Find the following products.
-24
64
30
14
-4
-49
To determine the signs in a division problem, recall that
This suggests that
What is
What is
What is
We have the following rules for dividing signed numbers.
Dividing signed numbers:
Find the following quotients.
Since the numbers have opposite signs, the quotient is negative.
Thus
Since the numbers have the same signs, the quotient is positive.
Thus,
Since the numbers have opposite signs, the quotient is negative.
Thus,
Find the following quotients.
4
-6
-2
3
Find the value of
Using the order of operations and what we know about signed numbers, we get,
Find the value of
14
Calculators with the
key can be used for multiplying and dividing signed numbers.
Use a calculator to find each quotient or product.
Since this product involves a
| Display Reads | ||
| Type | 186 | 186 |
| Press |
|
-186 |
| Press | × | -186 |
| Type | 43 | 43 |
| Press |
|
-43 |
| Press | = | 7998 |
Thus,
| Display Reads | ||
| Type | 158.64 | 158.64 |
| Press | ÷ | 158.64 |
| Type | 54.3 | 54.3 |
| Press |
|
-54.3 |
| Press | = | -2.921546961 |
Rounding to one decimal place we get -2.9.
Use a calculator to find each value.
1,108.08
1.226
-0.001
Find the value of each of the following. Use a calculator to check each result.
16
32
-36
-60
-12
3
-13
9
-5
11
28
-4
-12
-4
-6
15
49
-140
-7
-3
-5
13
((Reference)) Use the order of operations to simplify
((Reference)) Find
((Reference)) Write this number in decimal form using digits: “fifty-two three-thousandths”
((Reference)) The ratio of chlorine to water in a solution is 2 to 7. How many mL of water are in a solution that contains 15 mL of chlorine?
((Reference)) Perform the subtraction
"Used as supplemental materials for developmental math courses."