LO: to add decimalsType your name and send:

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The Basic Steps:

• Line up the numbers by the decimal point.

• Fill in missing places with zeroes.

• Add or subtract.

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Addition PropertiesCommutative Property of Addition: Numbers can be added in any order.

Example: 5+3=3+5

Associative Property of Addition: Numbers can be grouped in any way.

Example: (7+3) + 5 = 7 + (3+5)

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Find the nearest nice number

• Addition properties can be used to quickly find sums.

• Example: What is 52 + 12.4 + 48?• We can use an addition property to

quickly add this. • First, change the order: 52 + 48 + 12.4

________________ property.• Then, group the easy numbers together:

(52 + 48) + 12.4________________ property

• 100 + 12.4 = 112.4

commutative

associative

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Why Estimate?

• Before adding your numbers, use one of the estimating strategies you learned to see what the answer should be close to.

• When you add, you can see if your answer is reasonable.

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Example: 28.9 + 13.31

28.913.31+

0

42.21

• Line up the numbers by the decimal point.

• Fill in missing places with zeroes.

• Add or subtract.

This can estimate to 30 + 13, which is 43. (nearest nice numbers)

The answer is close to the estimate.

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Now your turn.

For the sum: 125.33 + 6.9

What would your estimate be?

a)118b)132c)131

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For the sum: 125.33 + 6.9{estimate is 132}

Which number should you write first?

a)125.33b)6.9c)It does not matter

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For the sum: 125.33 + 6.9{estimate is 132}

I write down 125.33 what do I do next?

• Line up the numbers by the decimal point.

• Fill in missing places with zeroes.• Add or subtract.

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For the sum: 125.33 + 6.9{estimate is 132}

What do you need to do now?

125.336.9+

A. AddB. SubtractC. Stick zero in if you

have any gaps0

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For the sum: 125.33 + 6.9{estimate is 132}

What do you need to do now?

125.336.90+

A. AddB. SubtractC. Stick a decimal in

underneath then relax

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For the sum: 125.33 + 6.9{estimate is 132}

Finally add to give the answer?

125.336.90+

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For the sum: 125.33 + 6.9{estimate is 132}

Finally add to give the answer?

125.336.90+

132.23

Is this near to your estimate?

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I really understand this and I got most of them correct.

I am beginning to understand this and I got many of them correct.

I need more practice to help me understand this and I made lots of mistakes.A

B

C

LO: to add with decimals.Last Last SlideSlide