ch11notes.notebook
January 23, 2015
11.1 Explore Addition and Subtraction With Decimals
How would you write 0.34 as a fraction? What do you say as you read 0.34? Thirty­four hundredths
That's easy to write as a fraction! Jan 23­9:35 AM
What if I have a number with one decimal place and another with two decimal places?
0.5 + 0.32
0
5
10
32
+ 100
We can't add these!! Why not?!!?!
It's an easy fix! Just "Add Nothing!" Jan 23­9:47 AM
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11.2 Adding Decimals
Jan 23­10:57 AM
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How to Add Decimals
Step
Example #1
73.569 + 24.47=
1) Write the problem
vertically. Line up the
decimals!
73.569
+24.47
2) Bring down the
decimal.
73.569
+24.47
.
Mar 19­7:45 AM
How to Add Decimals
Step
3) Add starting on the
right side of the
problem. Note: If there
is no number, add an
imaginary zero. Regroup
if needed.
Example #1
1
73.569 + 24.47=
1
73.569
+24.47
9 8 .0 3 9
Let's try some other problems using
manipulatives to help you conceptually
understand adding decimals. Click
here to begin!
Mar 19­7:45 AM
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11.3 Subtracting Decimals
What are the important rules to follow when subtracting? Jan 25­10:02 AM
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Now lets do a subtraction. You can use the same technique with the line to do decimal subtraction.
Lets do an example. Press the numbers below.
28.694 ­ 14.201
1
Write down the first number
2
Draw a line through the decimal point and line up
the next number with it
3
Subtract the numbers in a
vertical line as shown
. 694
14 . 201
14
54
28
­
14
493
Images and content are copyright to Intel PLS
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11.4 Estimating Sums and Differences
When we estimate to find a sum or difference, what must we do first? What are the rules when we do this? Jan 25­11:00 AM
Steps for Rounding Decimals
Step 1: Find the rounding place.
6.2
Step 2: Look at the digit to
the right. If it is 5 or more,
change to the next greatest
digit. If it is less than 5, leave
the number as is.
6.2
6.2 rounded to the nearest whole number is
6
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