How do you subtract with fractions or mixed numbers by decomposing?
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Transcript of How do you subtract with fractions or mixed numbers by decomposing?
How do you subtract with fractions or mixed numbers by decomposing?
3 - = 3 - 1 2 -
In this lesson you will learn how to subtract with
fractions or mixed numbers by decomposing.
Let’s Review
We know that equivalent fractions show equal amounts.
= = = = =
This could go on forever!
How do I decide which equivalent fraction to use?
Let’s Review
Whole numbers can be decomposed as fractions or mixed numbers.
=
= =
The possibilities are endless!
1 22=
1 2 1 33
4 =5 4 =33
Let’s Review
Mixed numbers like 1 can be decomposed into their individual parts.
1
= +
A Common MisunderstandingForgetting to decompose.
≠
4 - 1 = 24 - 1≠ 3
Core Lesson
Think about cookies.
I need to subtract
Mom says I can eat the cookies if I give my sister
of a cookie.
I’ll cut just one cookie making two halves.
I don’t want to cut all the cookies.
Now I have 2 + I can easily subtract .
3 = 2
2 cookies
-
Core Lesson
This works with a fraction bar model.
3
2
- 12
12
11
= 2
=-
Core Lesson
This works with mixed numbers.
2
1
- =
= -
14
1414
14 I need to take
away one half, but the
minuend isn’t divided in
halves.
I will use an equivalent fraction.
=
I need to subtract from 2
I need to decompose into more pieces.
I will decompose one of the wholes
into .
When one denominator is a
divisor of the other, only one fraction
has to be changed.
= 1 + + = 2= 1
= 1
14
= 1
Core Lesson 3 - 1
3- 1
I need to subtract 1
I need to decompose one of the wholes
into .
= 2
= - 1 13
1
1
13
13
1
In this lesson you have learned
how to subtract with fractions or mixed numbers
by decomposing.