Lesson: Adding and Subtracting Proper Fractions

Multiple Choice

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(you will need to take a picture and upload it at the end)

• YES I have my notebook out

• No, I know it means a bad grade

Adding and Subtracting Proper Fractions

Objective: Add and Subtract Fractions

Multiple Choice

What is the Least Common Multiple of 8 and 6.

• 16

• 12

• 24

• 8

• 48

​EXAMPLE

When we are adding or subtracting fractions it is easy when the whole is divided into the same number of parts. The example below has both wholes broken into 6 even parts.

​EXAMPLE

BUT...when we are adding or subtracting fractions it becomes more complicated when the whole is divided into a different number of even parts. The example below has one divided into 2 even pieces and the other into 4.

​Continued on next slide

​EXAMPLE

We need to rewrite the fractions so they are divided into the same number of parts

​EXAMPLE

​Least Common Multiple

​The smallest positive multiple that two or more numbers share.
Example: the multiples of 3 are 3, 6, 9, 12, ...

​EXAMPLE:

​What is the LCM of 6 and 8?

Multiples of 6: 6, 12, 18, 24, 30, 36, 42, ...
Multiples of 8: 8, 16, 24, 32, 40, 48, 56, ...

​EXAMPLE

​What if we don't have pictures.

​1) Find the Least Common Multiple for the denominators.

​2) Rewrite the fractions using the LCM as the denominator

​3) Perform the operation

​4) Simplify your answer if necessary

Multiple Select

Which expressions below are equivalent to: $$\frac{1}{3}+\frac{4}{5}$$

• $$\frac{5}{15}+\frac{12}{15}$$

• $$\frac{10}{30}+\frac{24}{30}$$

• $$\frac{1}{15}+\frac{4}{15}$$

• $$\frac{10}{30}+\frac{40}{30}$$

Math Response

Perform the operation:  $$\frac{3}{4}+\frac{1}{6}$$  

Type answer here

Correct Answer: \frac{11}{12}

Deg^°

Rad

​EXAMPLE

​What if we don't have pictures.

​1) Find the Least Common Multiple for the denominators.

​2) Rewrite the fractions using the LCM as the denominator

​3) Perform the operation

​4) Simplify your answer if necessary

Math Response

Perform the operation:  $$\frac{2}{5}-\frac{11}{20}$$  

Type answer here

Correct Answer: -\frac{3}{20}

Deg^°

Rad

​EXAMPLE

​What if we don't have pictures.

​1) Find the Least Common Multiple for the denominators.

​2) Rewrite the fractions using the LCM as the denominator

​3) Perform the operation

​4) Simplify your answer if necessary

Math Response

Perform the operation:  $$\frac{8}{9}+\frac{2}{3}$$  

Type answer here

Correct Answer: 1\frac{5}{9}

Deg^°

Rad

Open Ended

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