A positive number is any number that is greater than zero and has a positive sign ( + ).
Often the positive sign is understood and not written in front of the number. For
example, the number +8 is usually written as 8. A negative number is any number
that is less than zero and is written with a negative sign (-). For example, a negative
e ight is written as -8.
Multiplication a nd Division of Positive and Negative Numbers
When two positive numbers or two negative numbers are multiplied, the answer is
positive(+).
2 X 3 = 6 The + sign ( +6) is understood.
(-2) X (-3) = 6
When a positive number and a negative number are multiplied, the answer is negative (-).
2 X (-3) = -6
(-2) X 3 = -6
The rules for the division of positive and negative numbers are the same as the rules
for multiplication. When two positive numbers or two negative numbers are divided, the
answer is positive ( + ).
6
- = 2
3
-6 - = 2
-3
When a positive number and a negative number are divided, the answer is negative (-).
-6 6 - = -2 – = -2
3 -3
Addition of Positive and Negative Numbers
When positive numbers are added, the sign of the answer is positive.
3 + 4 = 7 The + sign (+7) is understood.
When negative numbers are added, the sign of the answer is negative.
-3 + (-4) = -7
When a positive number and a negative number are added, the smaller number is subtracted
from the larger number, and the result has the same sign as the larger number.
12 + (-15) = -3
Subtraction of Positive and Negative Numbers
When two numbers are subtracted, change the sign of the number to be subtracted and
follow the rules for addition shown above.
12-(+5) = 12- 5 = 7
12- (-5) = -12 + 5 = -7
Calculator Operations
On your calculator, there are four keys that are used for basic mathematical operations. The
change sign I+/-) key is used to change the sign of a number.
To practice these basic calculations on the calculator, work through the problem
going from the left to the right, doing the operations in the order they occur. If your calculator
has a change sign l+t-1 key, a negative number is entered by pressing the number
and then pressing the change sign
