Transcript Let`s Estimate!

Let’s estimate when we
multiply decimal fractions!
This is one way to check our
products.
Find 12 x 0.48 by rounding.
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
Round the 12 to 10
Round the 0.48 to .5
Now, let’s multiply.
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10 x .5 = 5.0
Our answer should be near 5
according to our estimation.

Let’s multiply:
0.48
x 12
96
+ 480
5.76
Since the estimate is 5, place the decimal
point so there is a one-digit whole
number in the product.
Count Decimal Places
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Let’s multiply:
0.48
x 12
96
+ 480
5.76
Since we had two decimal places in
our factors, we have to have two
places in our product.
Let’s count decimal places,
again.
Find the product of 0.7 x 0.5
Multiply as you do with whole
numbers.
0.7
x 0.5
0.35
Count the decimal places in each
factor. There are 2 decimal places in
the factors. We need 2 decimal
places in the product.
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Your turn.

Estimate by rounding.
0.4 x 1.7 =
What should you do first?
Estimation
Let’s round 0.4 to 0.5
 Next, round 1.7 to 2
 Now, let’s multiply.
0.5 x 2 = 1.0
Let’s check our answer. It should
be near 1.
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Count the decimal places to
multiply.
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Multiply:
.4
x 1.7
28
40
.68
There are 2 decimal places in our factors. We
have to have 2 decimal places in our
product. .68 would round to 1.0
Your turn again.
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How many decimal places will
be in the product for these
factors?
2.5 x .07
Count .5 and .07
There will be 3 decimal places in
the product.