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Use Addition and Subtraction Equations to Solve Problems

6th | Math

Goal

Vocabulary

Vocabulary

When you subtract the same amount to both sides of an equation and the two sides will remain equal.

Subtraction Property of Equality

When you add the same amount to both sides of an equation and the two sides will remain equal.

​Addition Property of Equality

If each square is equal to 1 unit, and the triangle labeled x is an unknown weight then the quantity on the left equals 9 and the quantity on the right is x + 4.

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9 units

9 = x + 4

x + 4 units

9 units

9 = x + 4

9 - 4 = x + 4 - 4

5 = x​

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The weight of the triangle is 5 units.​

x + 4 units

​Subtraction Property of Equality

You should write all of this down in your notebooks.

Where 6 is how tall the plant started, x is how much it grew, and 14 is how tall it was after 2 weeks.

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Think: What can we do to solve for x (how much did the plant grow in 2 weeks?)

6 + x = 14

Subtraction Property of Equality

6 + x = 14

6 - 6 + x = 14 - 6

x = 8​

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You should write all of this down in your notebooks.

We subtract 8.50 from both sides to get m by itself.

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Sara made $11.75 babysitting.​

8.50 -8.50 + m = 20.25 - 8.50

m = $11.75​

$8.50 + m = $20.25

Sara had $8.50 in her pocket. She earned m dollars babysitting and now she has $20.25. How much did she earn babysitting?

Explanation

x - 7 = 12

YES! We would add 7 to both sides.

x - 7 + 7 ​= 12 + 7 This is the Addition Property of Equality.

x = 19​

6th | Math

Addition Property of Equality

Let's check your understanding.

4 Questions

" If there is time left over, do your homework."