Vocabulary
This expression shows what property of addition:
3.2+(6+2.6) = (3.2+6)+2.6
Associative Property
Write an equation to represent the sum or difference shown on the number line (see the board).
-9+7
=-2
12.7-(-8.3-6.3)
27.3
8 - 3 + (-4)
8 - 3 - 4
5 - 4
1
1. Adjust signs
2. Subtract across
Dino is learning to scuba dive. First, he descended 27.75 feet. After ten minutes, he descended another 9.45 feet. Write and evaluate an expression to determine his elevation relative to sea level.
-27.75-9.45
-37.2ft
What is this showing?
|-3.8| = 3.8
Absolute Value
It was 34 degrees in the morning, it decreased 12 degrees by the evening. What is the correct addition expression?
34 + (-12)
-2.30-(-8 1/10)
5.8
-351-53
|351| + |53|
-404
1. Find the absolute value
2. Add
3. Make the answer negative
Ami has $138.62 in her account at the beginning of the week. He wrote the following transactions for the week:
$76.00, -$235.21, $108.54
What is Ami's account balance at the end of the week?
1. Write an expression
2. Adjust the signs
3. Add/Subtract to solve
138.62+76.00-235.21+108.54
$87.95 left in the account
If you subtract a negative integer, it becomes...
Positive
What is an equivalent addition expression:
-92 - (-32)
-92+32 or 32+(-92)
15.8-(-2 1/4) + (-6)
12.05
Explain why you might want to use properties to change the order and grouping of the numbers in the following sum. -45.2 + (-7.9) + (-3.8)
Answers will vary
A rock climber ascends 18 3/4 feet to the top of a rock ledge. The climber descends 8 1/8 ft and takes a break. Write and evaluate an addition expression to tell how much farther the climber must descend to reach the original level.
18 3/4 + (-8 1/8) =
18 6/8 - 8 1/8 +
10 5/8ft
What do you call the numbers being added together and the answer to an addition question?
addends, sum
The lowest temperature of the day was -4.8 degrees. The highest temperature of the day was 23.71 degrees. Write an equation to find the difference.
23.71-(-4.8)
or 23.71+4.8
-3 1/2 + 8 3/4 - (-1.75)
7
12.4 + 38 4/5
12 4/10 + 38 4/5
12 2/5 + 38 4/5
50 6/5
51 1/5
1. Convert to like numbers
2. Convert to same denominator
3. Add
4. Simplify
Christian needs 18 2/5 feet of fence to complete his garden. He has lengths of fencing that are
4 2/5 ft, 6.78 ft, and 5 1/4 ft long.
Does he have enough fencing to complete the project? Why? How much is leftover or how much more does he need?
1. convert amounts to decimals
2. Add the amounts
3. Subtract to see if enough
4.4+6.78+5.25
18.4-16.43=1.97
He has enough. He was 1.97ft extra fencing.
What do you call the numbers in a subtraction sentence?
On Monday Jamie dug a hole 35 feet. On Tuesday, she continued to dig 12 more feet. On Wednesday, she filled in 6 ft of her hole. Write an expression.
-35+(-12)+6
or
-35-12+6
15 1/4 - (7 1/2 +5.25) + 4 3/4
7.25
Keith buys 3 yards of material to make a blanket. He trims a total of 1/6 yard off before sewing. How much material is left?
3 yards, -1/6 yards
3+(-1/6)
2 and 2/2 + (-1/6)
2 and 6/6-1/6 = 2 and 5/6
2 5/6 yards are left.
1. Read the problem, identify the quantities
2. Reread the problem, identify the operation
3. Reread the problem to identify what it wants you to do.
4. Write the expression
5. Convert the denominators
6. Subtract to solve
A cake mix recipe calls for 2 1/4 cups of sugar. The recipe requires 1/8 cup less oil than sugar and 3/4 cup more flour than sugar. How many cups are in this recipe?
1. Find the amount of each ingredient
2. Convert to be same denominators
3. Add/Subtract and simplify
Sugar: 2 1/4
Oil: 2 1/4-1/8 (=2 1/8)
Flour: 2 1/4+3/4 (=3)
(2 1/4+2 1/8) + 3
2 2/8+2 1/8=4 3/8
4 3/8+ 3 = 7 3/8 cups