Adding and Subtracting Decimals

Adding and Subtracting Decimals

Open Ended

What is one question you'd like answered about decimals as we begin today?

Rules for adding and subtracting decimals

• if the signs are the same, just add

• if the signs are different, subtract and take the sign of the larger absolute value

• when subtracting a negative, just add the opposite

Multiple Choice

What was the first rule?

• When subtracting a negative, add the opposite

• If the signs are different, subtract and take the sign of the larger absolute value

• When the signs are the same, just add

when the signs are the same

Just add the two numbers together
For example -4.3 + -8.2 = - 12.5
or -2.7 - 9.1 = - 11.8

Fill in the Blank

-3.2 + -7.5 =

Fill in the Blank

-9.42 - 4.14 =

If the signs are different

Subtract and take the sign of the larger absolute value

14.2 - 17.8 = - 3.6

-4.9 + 7.2 = 2.3

Fill in the Blank

-7.9 + 5.4

Fill in the Blank

8.1 + (-2.8) =

When subtracting a negative

just add the opposite

7.3 - (- 1.7) = 7.3 + 1.7 = 9.0

-2.4 - (- 3.2) = -2.4 + 3.2 = 0.8

Fill in the Blank

8.7 - ( - 2.1 ) =

Multiple Select

What are the three things we just said to do when adding or subtracting decimals

• If the signs are different, subtract the numbers

• If the signs are different, add the numbers together

• When subtracting a negative, just add the opposite

• When the signs are the same, add the numbers together

Open Ended

What is one question you have about today's lesson you'd like answered?