Signed numbers, also called integers, are numbers that show not only how far a number is from zero on a number line, but which side of zero it is on. A number that is 3 less than zero is -3 and a number that is 3 more than zero is 3.
Adding and Subtracting Integers
If you have two numbers that are the same sign being added together, you add them and keep the sign the same. 3 + 5 = 8. Also, -3 + -5 = -8. If the signs are different, subtract and keep the sign of the larger (further from zero) number. -3 + 5 = 2; and 3 + -5 = -2. Also any number following a subtraction sign is negative, so 3 + -5 is the same thing as saying 3 – 5.
Multiplying and Dividing Integers
When multiplying or dividing integers, you multiply or divide as you normally would, then follow this rule for determining the sign: If the signs are the same, the answer is positive. If the signs are different, the answer is negative. Therefore: 3 • 5 = 15 3 • -5 = -15 -3 • 5 = -15 -3 • -5 = 15
Absolute value is a measure of how far a number is from zero on a number line regardless of which side of zero it is on. We show absolute value by putting these lines around a number: |3|. The absolute value of a number is always positive, so |3| = 3 and |-3| = 3.