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Practice Multiplying Decimals by a 2-Digit Number
31.7 x 1 3
9 5 1+ 3 1 7 0 4 1 2 1
1 decimal place
1 decimal place
Evaluate: 31.7 x 13
8.20 x 34
3 2 8 0 +2 4 6 0 0
2 7 8 8 0
2 decimal places
2 decimal places
Evaluate: 34 x 8.20
42.3 x 1 7
2 9 6 1+ 4 2 3 0 7 1 9 1
1 decimal place
1 decimal place
Evaluate: 17 x 42.3 21
1
2.132 x 14
8 5 2 8 +2 1 3 2 0
2 9 8 4 8
3 decimal places
3 decimal places
Evaluate: 14 x 2.132 1
7.35 x 25
3 6 7 5 +1 4 7 0 0
1 8 3 7 5
2 decimal places
2 decimal places
Evaluate: 7.35 x 25 21
1
57.6 x 1 4
2 3 0 4+ 5 7 6 0 8 0 6 4
1 decimal place
1 decimal place
Evaluate: 14 x 57.6 23
1
Directions:Quietly, put your markers, boards, and erasers back into the bin. We will use them later.
Open up to your table of contents.
Multiplying with Decimals
Multiplying Whole Numbers
25 x 12
Multiply: 25 x 12
1. Multiply the ones 502. Multiply the tens + 2503. Add the products 300
Hmmm but what if 12 was 1.2?
What do you notice about the changeof 12 to 1.2??
If we compared the answer of 25 x 12and the answer of 25 x 1.2, which answer do
you think would be bigger and why?
Multiply: 25 25 x 12 x 1.2 5 0 5 0 +2 5 0 +2 5 0 3 0 0 3 0 0
Multiply: 25 no decimal place
x 1.2 1 decimal place 5 0
+2 5 0 3 0 0
1 decimal place
Multiply: A 52 no decimal place
x .31 2 decimal places 5 2
+1 5 6 0 1 6 1 2
2 decimal places
Multiply: B 1.4 1 decimal place
x 5.6 1 decimal place 8 4
+7 0 0 7 8 4
2 decimal places
Place the decimal point in the product
A 23.5x 6
1 4 1 0
Place the decimal point in the product
B 6.65x 4
2 6 6 0
Place the decimal point in the product
C 54.1x .7
3 7 8 7
Place the decimal point in the product
D 1.89x .5
9 4 5
How many times do you move the decimal???A) 4 x .25
Two Decimal PlacesB) 9.8 x 7
One Decimal PlaceC) 25.3 x 21.5
Two Decimal PlacesD) 87.3 x 5.66
Three Decimal PlacesE) .289 x 4.2
Four Decimal Places
Moving the Decimal the CORRECT NUMBER of Places
One Decimal Place Two Decimal Places
Three Decimal Places Four Decimal Places
Let’s Begin…
2. 6X 7
. 4 6X 2
1 6 . 8 X 1 2
1. 4 5 8 X 4
. 7 5X 7
35.6 X 9
1 6. 0 1 X 1.1
.6 5 4X 2 .9
.62X8.4
.7 1 2X 3.2
. 4 6X 2
2. 6X 7
1. 4 5 8 X 4
. 7 5X 7
35.6 X 9
1 6. 0 1 X 1.1
.6 5 4X 2 .9
.62X8.4
.7 1 2X 3.2
1 6 . 8 X 1 2
One Decimal Place Two Decimal Places
Three Decimal Places Four Decimal Places
Your turn to try it out!
Multiplying with Decimals
Place the decimal point in the product
A 42.7x .3
1 2 8 1
Place the decimal point in the product
B 4.23x .8
3 3 8 4
Place the decimal point in the product
C 1.23x .54
6 6 4 2
Independent Practice
Multiply: 34
x 1.7 2 3 8
+3 4 0 5 7 8
no decimal place 1 decimal place
1 decimal place
Multiply: 52
x .29 4 6 8
+1 0 4 0 1 5 0 8
no decimal place 2 decimal places
2 decimal places
Multiply: 7.3
x 2.5 3 6 5
+1 4 6 0 1 8 2 5
1 decimal place 1 decimal place
2 decimal places
Multiply: 9.2
x .24 3 6 8
+ 1 8 4 0 2 2 0 8
1 decimal place 2 decimal places
3 decimal places
Multiply: .37
x .82 7 4
+2 9 6 0 3 0 3 4
2 decimal places 2 decimal places
4 decimal places
Wrap -Up
Why would the answer to …
250 And 250X 3.4 x 34
be different even though they have the same numbers?
Make it easy with….
ESTIMATION!
iPod Nano- 4th generation $89.99
What if you and your 2 friends wanted to buythe iPod Nano, about how much would it cost?
$89.99 x 3
$90 x 3Estimate: $270
Kodak Camera SALE $77.75
What if you wanted to buy the last 2 Kodak Cameras that were left on the shelf, about how much would it cost?
$77.75 x 2
$80 x 2Estimate:$160
Gas PricesOne gallon of Unleaded gas costs $3.61
The car you ride in needs 9.5 gallons of gas to be at a FULL TANK.
About how much money would be spent to fill up the car’s tank?
9.5 x $2.7510 x $3
Cost would be about $30
Gas Prices1 gallon of Unleaded gas costs $3.61
What if you needed 15.6 gallons for a FULL TANK?
About how much money would it take?
15.6 x $2.7520 x $3
Cost would be about $60
