Slobodanka

middle grade 8th

What is a Common Denominator?
Thanks



Hi Slobodanka,

We say that two fractions have a common denominator if both fractions have the same denominator. This is important when you add or subtract two fractions. For example if you want to add  3/4 and  1/6 you need first to exprress both fractions with the same denominator. That is you need to find a common denominator.

A denominator that will work is 12 since

 1/6 = 2/12 and  3/4 = 9/12

Thus

 1/6 +  3/4

= 2/12 + 9/12

= 11/12

How did I know that 12 is a common denominator?

The denominators of the two original fractions are 4 and 6 and what I noticed is that 12 is a multiple of both 4 and 6. This means that I can express both fractions with a denominator of 12.

I hope this hepls,
Penny

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