Most of the time in everyday life we deal with positive numbers, so your skills in dealing with negative numbers are probably rusty. Statistics is an area where we use many negative numbers, so you need to brush up on the rules. Recall something you learned a long time ago: the number line.
________________________|__________________________ -6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6
On the number line, negative numbers run to the left of zero, and positive numbers run to the right of zero. The bigger a negative number, the further you are getting from zero and the “deeper in the hole” you get.
When a number is shown without a sign, it is assumed positive. The negative sign will precede negative numbers.
Apply the following rules when working with negative numbers:
One: When you multiply or divide numbers with different signs, the result is negative.
Two: When you multiply or divide numbers with the same signs, the results are always positive. This also means that when you square a negative number, the result will always be positive.
Three: when you add up a series of negative numbers, the result is negative.
Four: When you add a positive number and a negative number, ignore the sign and treat it as a subtraction problem, subtracting the smaller from the larger. The result takes on the sign of the larger number.
Five: If you have a series of numbers with mixed signs that need to be added together, sum all of the positive numbers, then sum all of the negative numbers, then use rule four above to determine the final sum.
Six: When you subtract a negative from a negative, ignore the sign and subtract. The result is negative.
Example: -10 - -4 = -6
Seven: When you subtract a negative number from a positive number, the negative number becomes a positive number and the numbers are added together.
Example: 5 - -5 = 10
Eight: When you subtract a positive number from a negative number, ignore the signs and add the numbers together. The answer is always negative.
Example: -6 – 4 = -10
Last Modified: 06/28/2018