D multiply-decimals

Weekly Problem
copyright©amberpasillas2010

On average, a human hair
grows about 1.25
centimeters per month. At
this rate, how long would a
strand of hair grow in two
years?

DECIMALS
Rounding Decimals Review
and
Multiplying Decimals

___ , ___ ___ ___ ___ ___ ___ ___
Thousands
Hundreds
Tens
Ones
Tenths
Hundredths
Thousandths
TenThousandths
5 1 8 2 1
Read as 518 and 21 hundredths
Decimals are read as “and”
Rounding Review

Find the number. Circle it.
Look next door.
4 or less just ignore.
5 or more add one more.
Example: Round 5368 to nearest hundreds.
Circle the 3 in the hundreds place.
Look next door at the 6.
It is 5 or more so add 1 more to the
hundreds place.
5368 rounds to 5400
Rounding Review

Round to the
nearest tenths
2.876
2.9
Round to the
nearest hundredths
31.6999
31.70
Rounding Review

Round to the
nearest tenths
3.478
3.5
Round to the
nearest hundredths
22.5972
22.60
Rounding Review

Steps for Multiplying Decimals
Step 1: Write the problem vertically.
Step 2: Ignore the decimal point(s) and multiply.
Step 3: Determine where the decimal point
goes in the product.
Place the decimal point in the answer
by counting how many places the
decimal point has moved.

Multiply 3 x 0.14
0.14 3 x 0.14
=
0.42

Multiply 3 x 0.14
2
Step 1: Write the problem vertically0.14
x 3 Step 2: Ignore the decimal points
and multiply
Step 3: Determine where the decimal
point goes in the product.
The decimal moves two places to the left
1
40
0.42

Multiply 5 x 0.18
0.18 5 x 0.18
=
0.90

Multiply 5 x 0.18
0
x 5 Step 2: Ignore the decimal points
and multiply
4
90
0.90

Multiply 0.2 x 0.6
0.2 0.6
=
0.2

Multiply 0.2 x 0.6
0.2 0.6
=
0.2 x 0.6

Multiply 0.2 x 0.6
0.2 0.6
=
0.2 x 0.6
= 0.12

Multiply 0.2 x 0.6
2
x 0.6 Step 2: Ignore the decimal points
and multiply
10
0. 12

Multiply 0.4 x 0.7
0.4 0.7
=
0.4

Multiply 0.4 x 0.7
0.4 0.7
=
0.4 x 0.7

Multiply 0.4 x 0.7
0.4 0.7
=
0.28

Multiply 0.4 x 0.7
8
x 0.7 Step 2: Ignore the decimal points
and multiply
20
0. 28

200
x .25
0
+
5000
0
001
004
Move the
decimal
two places
to the left in
your answer.
.

HOW MANY DECIMAL PLACES?
1 decimal place3.1
2) (0.4)(2.53)
0.4
 2.53
1) 3.1(0.28)
1.012
 0.28 2 decimal places
0.868 1 + 2 = 3 decimal places
1 decimal place
2 decimal places
1 + 2 = 3 decimal places

1) 0.16
x 30
000
084
084
1
2) 70
x 1.2
041
007
048
+
3)
1
0.0048
x 32
690
044
635
1
1
1
2
0
0
1
0

Evaluate The Power
An exponent tells how many times a
number is multiplied by itself.
3
4
Base
Exponent
3 is written as 3 • 3 • 3 • 3 = 81
4
This exponent is read three to the fourth power.

Evaluate The Power
Evaluate (0.2)2
4
This means (0.2)(0.2)
0.2
x 0.2
The decimal goes moves two places to the left
00
0. 04

Calculate Area With Decimals
4 in.
0.58
in.
Area = base x height
Multiply 4 x 0.58
2
0.58
x 4
The decimal
moves two
places to the
left.
3
32
2.32 in
2
2
Area is
square units!

THE END!!!
Take out your study guide

Multiply 0.4 x 0.14
6
Step 1: Write the problem vertically
0.14
x 0.4
Step 2: Ignore the decimal points
and multiply
The decimal moves 3 places to the left.
1
50
0.056
Multiplying Decimals#5
0

Evaluate The Power
Evaluate (0.5)2
5
This means (0.5)(0.5)
0.5
x 0.5
The decimal
moves two
places to the left. 20
0. 25
#6
2

2 in.
0.98 in Area = base x height
# 7
Multiply 2 x 0.98
6
0.98
x 2
The decimal
moves two
places to the
left.
1
91
1.96 in
2
1
Area is
square units!
The Area (A) is the number of square units
needed to cover a figure.

D multiply-decimals

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