Adding fractions with unlike denominators

Adding Fractions With Unlike Denominators

Vocabulary

• denominator-bottom number in a fraction

• numerator-top number in a fraction

• multiple-the product of one number multiplied by another number.

• sum-answer to an addition problem

• Least Common Multiple(LCM)-smallest number both numbers will evenly divide into

Multiple Choice

The number on the bottom of a fraction is called what?

• numerator

• denominator

• equivalent

• improper

Multiple Choice

The number on the top of a fraction is called what?

• numerator

• denominator

• fractionator

• equivalent

Remember...

• You can only add or subtract fractions when they have the same denominators.

• The first step is to find the LCM.

• Skip count to find the first number they have in common.

Multiple Choice

What does LCM stand for?

• Lowest Common Magician

• Least Common Multiplier

• Least Common Multiple

• Lowest Community Maker

Multiple Choice

What is the first step in solving this problem?

⅘ + ½ =

• Add the top parts of the fraction

• Rewrite the fractions in the simplest form.

• Find a common denominator by finding the LCM.

• Make each fraction into an improper faction.

Multiple Choice

What is the LCM for 3 and 9?

• 3

• 9

• 27

• 18

Multiple Choice

What is the LCM for 4 and 7?

• 4

• 7

• 14

• 28

Multiple Choice

Danny added the following fractions incorrectly. What was the first step that Danny needed to take to add the following fractions?

• Danny needs to find the Least Common Multiple to find the common denominator of the fractions before adding.

• Danny left his answer as an improper fraction.

• Danny did not make a mistake.

• Danny forgot to reduce.

Next step,

• After you find the LCM, replace the old denominator with the new one, making a new fraction.

• The fractions need to stay equivalent.

• Multiply both the denominator and numerator by the same number.

• This will keep the fractions equivalent.

Multiple Choice

What do you call an equal fraction ?

• Equivalent fraction

• Mixed fraction

• Improper fractions

• Denominator

Multiple Choice

Complete the equivalent fraction.

• 6

• 9

• 15

• 23

Multiple Choice

Complete the equivalent fraction.

• 2

• 4

• 1

• 3

Multiple Choice

If you are adding the fractions ⅕ + ¾ , the LCM is 20. What are the new, equivalent fractions.

•  $\frac{1}{20}+\frac{3}{20}$  
  

•  $\frac{4}{20}+\frac{15}{20}$  
  

•  $\frac{10}{20}+\frac{15}{20}$  

•  $\frac{4}{20}+\frac{12}{20}$  

Once you have your common denominator and equivalent fractions, then you add the numerators.

• the denominators stay the same when adding

•  $\frac{2}{7}+\frac{2}{3}=\ \ \ \frac{6}{21}+\frac{14}{21}=\frac{20}{21}$  

Multiple Choice

 $\frac{2}{3}+\frac{1}{9}=$  First find the common denominator and then make new equivalent fractions. Last, add only the numerators. 

•  $\frac{7}{9}$  

•  $\frac{3}{12}$  

•  $\frac{5}{4}$  

•  $\frac{3}{27}$  

Multiple Choice

1/4 + 3/5

First find the common denominator and then make new equivalent fractions. Last, add only the numerators.

• 4/9

• 17/20

• 4/20

Multiple Choice

 $\frac{1}{4}+\frac{3}{8}=$  

•  $\frac{4}{8}$  

•  $\frac{5}{8}$  

•  $\frac{7}{5}$  

•  $\frac{4}{12}$  

Multiple Choice

Is this a correct answer?

• Yes, the student correctly added.

• No, you cannot add unlike denominators

• No, 5 + 7 is not 12

• No, 2 + 3 is not 5

Multiple Choice

Billy ate  $\frac{3}{8}$  of a pizza and Felicity ate  $\frac{1}{4}$  of the pizza. How much pizza did they eat in all?

• 1/2

• 5/8

• 3/4

Multiple Choice

Sometimes when you add your fractions, the numerator is greater than the denominator. This is called an _________ fraction.

• Mixed

• Different

• Proper

• Improper

Multiple Choice

When you have an improper fraction what do you do to make it a mixed number?

• Divide

• Multiply

• Add

• Subtract

Multiple Choice

Write the improper fraction as a mixed number

¹²/₄

• 3 ³/₄

• 3 ¹/₄

• 3

• 4

Multiple Choice

Write the improper fraction as a mixed number

²³/₅

• 4 ³/₅

• 4 ⁵/₃

• 5 ³/₄

• 4 ³/₄

Reducing

• The last step in adding fractions is to simplify or reduce if possible.

Multiple Choice

How do you reduce fraction?

• Multiply by a common factor of both the numerator and denominator.

• Divide by a common factor of both the numerator and denominator.

• Pick a random number and divide the fraction twice

• None of these are true

Multiple Choice

Reduce: 6/15

• 2/5

• 3/5

• 4/9

Multiple Choice

Reduce the fraction:

8/24

• 1/12

• 1/3

• 2/12

• 4/8

Multiple Choice

Reduce or Simplify 6/9.

• 2/3

• 3/3

• 9/6

• 1/9