Multiply Rational Numbers

Honors Math – Grade 7

When track season is over, Ms. Alaya decreases the distance of her weekday runs by 1.1 mi per week for three weeks in a row. What rational number represents the total decrease in Ms. Alaya’s runs for the three weeks?

What are the important facts?

Express the numbers as rational numbers.

What operation does the problem suggest?

KEY CONCEPT Multiply Two Rational NumbersTo multiply rational numbers:

1. If the factors have like signs, the product is positive!2. If the factors have unlike signs, the product is negative!

Remember to first multiply the rational numbers and then determine the sign

)2.9(7.13

)4.2(15.5

Remember when multiplying decimals to align the digits not the decimal points.

Also, remember to count the decimal places in each factor to determine the number of decimal places in the product!

5

4

11

9

20

15

30

24

Remember when multiplying two fractions, you may cancel any numerator with any denominator.

Also, all answers must be expressed in simplest form!

3

14

8

6

2

12

5

2

Remember when multiplying mixed numbers, to change the mixed numbers to improper fractions and then multiply using cancellation.

8

525.1

5

4

3

2

6

173