6th Grade Math Textbook, Fundamentals

 &KDSWHU

1-6

Update your skills. See page 412 XII.

Divide Integers

Objective To divide integers with and without models

Mrs. Ferrara drains water from her above-ground pool.
The height of the water decreases by 3 inches per minute.
How many minutes does it take for the height of the water
to decrease 15 inches?

To find the number of minutes,

divide:  15 (3)

You can use repeated subtraction

to model division.

Method 1 Use Tiles

 15 (3) (3) (3) (3) (3)

 15 (3)  5

Method 2 Use a Number Line

 15 (3)  5

So it takes 5 minutes for the height of the water to decrease 15 inches.

Multiplication and division are ; one undoes the other.

You can use this relationship to determine the rules for dividing integers.

The pattern above shows that the rules for dividing integers are similar to

the rules for multiplying integers.

Since there is no related multiplication sentence for any division sentence

with a divisor of 0, division by zero is said to be undefined. For example,

3 0 is undefined because there is no value of nthat makes n• 0 3 true.

 3  3 ^3 ^3 ^3

 16  15  14  13  12  11  10  9  8  7  6  5  4  3  2  10

Multiplication Sentence Related Division Sentence

3 • 6 18 18  6  3

3(6)  18  18 (6)  3

3(6)  18 18 (6)  3

3 • 6  18  18  6  3

inverse operations

Think

To drainmeans “to

decrease,” so use

15 to represent a

decrease of 15 inches.

 15 (3) means 15 separated into

equal groups of 3.