How to Multiply and Divide Positive and Negative Numbers

Multiplying and dividing are the easiest operations to do with positive and negative numbers. As long as you can multiply and divide, the rules for multiplying and dividing positive and negative numbers are not only simple, but they’re also the same for both operations:

  • When multiplying or dividing two numbers, if the two signs are the same, the result is positive, and if the two signs are different, the result is negative.

  • When multiplying and dividing more than two numbers, count the number of negatives to determine the final sign: An even number of negatives means the result is positive, and an odd number of negatives means the result is negative.

You multiply and divide positive and negative numbers “as usual” except for the positive and negative signs. So ignore the signs and multiply or divide, then, if you're dealing with two numbers, the result is positive if the signs of both numbers are the same, and the result is negative if the signs of both numbers are different.

Check out the following examples:

(–8) × (+2) = –16

So, 8 multiplied by 2 is 16, and because the signs of both numbers are different, the answer is negative, –16.

(–5) × (–11) = +55

So, 5 multiplied by 11 is 55, and because the signs of both numbers are the same, the result is positive, +55.

(+24) ÷ (–3) = –8

So, 24 divided by 3 is 8, and because both numbers have different signs, the result is negative, –8.

(–30) ÷ (–2) = +15

So, 30 divided by 2 is 15, and because both numbers have the same signs, the answer is positive, +15.

When multiplying and dividing more than two positive and negative numbers, use the Even-Odd Rule: Count the number of negative signs — if you have an even number of negatives, the result is positive, but if you have an odd number of negatives, the result is negative.

The following examples show you how to use the Even-Odd Rule:

(+2) × (–3) × (+4) = –24

This problem has just one negative sign. Because one is an odd number the answer is negative.

(+2) × (–3) × (+4) × (–1) = +24

Two negative signs mean a positive answer because two is an even number.

An even number of negatives means a positive answer.

Three negatives mean a negative answer.

Comments (1)

  1. Posted by maryp
    thanks. i was so confused before dummies.com now i can pass the test.

Leave a Reply


Post Comment

Connect with For Dummies

Sign Up for RSS Feeds

Education & Languages

Inside Dummies.com