Adding Integers

Lesson 10

1. Order the following from least to greatest:

3, −5, 5, 1, −2, −9 

Find the value of each expression.

2. 60.18 + 109.3

3. 7(5.7)

4. 14 ÷ 0.5

Target: Add two or more integers to find the sum.

Zero Pair: A positive chip and a negative chip paired together.

–1 + (– 4)

Using integer chips: Using a number line:

6 + (–3)

Using integer chips: Using a number line:

1. Determine the sign of the answers.• If both are positive, the sum is positive.• If both are negative, the sum is negative.• If there is one of each, the sum is the sign of the number

with the greatest absolute value.

2. Find the sum.• If integers have the same sign, add the absolute values and

use the sign determined above.• If integers have different signs, subtract the lesser absolute

value from the greater absolute value and use the sign determined above.

JaNell descended 16 feet and then rose 21 feet in elevation on a hike. Write an integer addition expression to represent this situation. Determine her overall change in elevation.

– 16 + 21 Determine the sign: |21| > | – 16| so the sign will be positive. Find the sum by subtracting and use the sign determined

above:◦ 21 – 16 = 5◦Answer: +5

JaNell’s overall change in elevation is 5 feet.

Find the value of –5 + (–2) + 1.

Find the sum of the first two numbers. –5 + –2 = –7

Add the third number to the sum. –7 + 1 = – 6

–5 + (–2) + 1 = –6

Find the value of each expression.

1. −5 + 2

2. 9 + (−8)

3. −2 + (−10)

4. −1 + (−4) + (−9)

5. 140 + (−122) + (−10)

Three methods for adding integers were introduced in this lesson (integer chips, number lines or integer rules). Which method do you prefer? Why?