Adding Fractions with Common Denominator

Adding Fractions/Using Common Denominators

Open Ended

Why do we have to have common denominators when adding fractions?

Common Denominators are necessary

• Because when adding fractions, you have to use numbers that are alike in nature.

• To be sure that you get an answer that is reduced to it's proper format, you need to find the LEAST common denominator.

Multiple Choice

Find the least common multiple between 6 and 8

• 48

• 24

• 32

• 72

Once you get the Least Common Denominator...

you have to multiply each fraction by one (represented by what it takes to make the denominators the same over itself). For example, in the case of 5/6 + 1/8, the Least Common Denominator we learned is 24. In order to make 5/6 into 24ths, we have to multiply 5/6 * 4/4, making it 20/24. For the 1/8, we must multiply it by 3/3, making it 3/24. Now you can add the like fractions together and come up with 20/24 + 3/24= 23/24.

Multiple Choice

What is the least common multiple of 7 and 9?

• 9

• 16

• 72

• 63

Multiple Choice

3/4 + 1/10 =

• 34/40

• 3/14

• 3/40

• 17/20

After you get your answer in fraction form...

• Make sure it is a proper fraction, meaning the numerator is not higher than the denominator. For example, if you added 3/4 + 1/2, you would come up with 5/4. This should be reduced to a proper mixed fraction and written as 1 1/4.

• Make sure that your answer is reduced to the lowest possible numerator and denominator. An example of this would be if you added 3/10 + 1/5, your least common denominator would be 10. you would not have to change the 3/10, but 1/5 would have to be multiplied by 2/2, making it 2/10. When you add 3/10 + 2/10 you would get 5/10 as your answer. However, 5/10 can be reduced to 1/2, because 5 goes into 10 2 times.

Multiple Choice

7/9 + 2/3 =

• 26/18

• 1 4/9

• 14/27

• 1,234,546/1,593,499

Poll

How would you rank your understanding of common multiples, least common denominators and adding fractions?

• I am a pro!

• I feel fairly confident.

• I still struggle a bit

• I am lost.

Thank you

Make sure you always get the least common denominator when adding fractions.