Add/Sub decimals and word problems Absent copy Mon 10 / 7

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# Add/Sub decimals and word problems Absent copy Mon 10 / 7 - PowerPoint PPT Presentation

Add/Sub decimals and word problems Absent copy Mon 10 / 7. Example 1. Add the decimal: 14 + (-3.2) 14 .00 - 3.2 0 10.8 Solution. Are the signs the same or different? They are different. What integer rule do we use?

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Presentation Transcript
Example 1

14 + (-3.2)

14.00

- 3.20

10.8

Solution

• Are the signs the same or different?
• They are different.
• What integer rule do we use?
• Subtract and give the sign of the larger.
• What do we need to do with the decimals in order to add/sub them?
• You have to line up the decimals when adding and subtracting.

10.8

Example 2

-13.2 + (-29.8)

29.8

+ 13.2

-43.0

• Are the signs the same or different?
• The signs are the same.
• What integer rule do we use?
• Add and keep the signs.
• What do we need to do with the decimals in order to add/sub them?
• We need to line up the decimals when adding and subtracting.

-43.0

Solution

Example 3
• Subtract the decimal:

-17 - (- 4.3)

17.00

- 4.30

-12.7

• What do we do first when we see a subtraction problem?
• Are the signs the same or different?
• The signs are different.
• What integer rule do we use?
• Different signs subtract and keep the sign of the larger #.
• What do we need to do with the decimals in order to add/sub them?
• We need to line up the decimals when we add and subtract.

-12.7

Solution

Example 4
• Subtract the decimals:

-14.3 - 4.2

14.3

+ 4.2

-18.5

• What do we do first when we see a subtraction problem?
• Are the signs the same or different?
• The signs are the
• What integer rule do we use?
• Same signs add and keep the sign they both have.
• What do we need to do with the decimals in order to add/sub them?
• We need to line up the decimals to add and subtract.

-18.5

Solution

Example 5
• From Kevin’s fort he wiggled his way east for 8.9 miles to the arcade. From the arcade he wiggled 2.5 miles due west to La Cocina. How far was he from his fort.

8.9 - 2.5 =

8.9

- 2.5

6.4

• What way does east or west go?

Up and down or right to left

• What operation are we going to perform when writing out the expression?
• We will use subtraction.
• What do we do first with a subtraction problem?
• What integer rule do we use?
• Different signs subtract and give the sign to the larger.

6.4 miles

Solution

An equation is shown.x + y = zGiven each equation, fill in each square with a correct value to make each a true statement. Assume x, y, and z are not 0.

Example 6

x

y

z

-x

-y

-z

y + = z

+ = - z

x

-x

-y