7th Grade Math

90 Integers

Add Integers with Different Signs

Find 7 + (-1).

7 + (-1) = 6 Subtract absolute values; 7 - 1 = 6. Since 7 has the greater absolute

value, the sum is positive.

Find - 8 + 3.

• 8 + 3 = - 5 Subtract absolute values; 8 - 3 = 5. Since -8 has the greater absolute
  value, the sum is negative.

Find 2 + (-15) + (-2).

2 + (-15) + (-2) = 2 + (-2) + (-15) Commutative Property (+)

= [2 + (-2)] + (-15) Associative Property (+)

= 0 + (-15) Additive Inverse Property

= - 15 Additive Identity Property

g. 10 + (-12) h. - 13 + 18 i. (-14) + (-6) + 6

ROLLER COASTERS The graphic shows the change in height at

several points on a roller coaster. Write an addition sentence to

find the height at point D in relation to point A.

+ 20

"

#

$

%

&

• 32

+ 16 -^10

20 + (-32) + 16 = 20 + 16 + (-32) Commutative Property (+)

= 36 + (-32) 20 + 16 = 36

= 4 Subtract absolute values. Since 36 has the

greater absolute value, the sum is positive.

Point D is 4 feet higher than point A.

j. WEATHER The temperature is -3°F. An hour later, it drops 6° and

2 hours later, it rises 4°. Write an addition sentence to describe

this situation. Then find the sum and explain its meaning.

Commutative Properties

a + b = b + a

a · b = b · a

Associative Properties

a + (b + c) = (a + b) + c

a · (b · c) = (a · b) · c

Identity Properties

a + 0 = a

a · 1 = a

086_098_C2L2_895130.indd 90 12/29/09 4:00 PM