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## Staging content lifeboat

### Course: Staging content lifeboat>Unit 14

Lesson 13: Decomposing fractions

# Decomposing a fraction visually

Sal uses a tape diagram to decompose 7/9. Created by Sal Khan.

## Want to join the conversation?

• How do you add numbers with different denominators (EXAMPLE: 3/9 + 2/6)? •  You would need to convert the fractions so that they have the same denominator, and then add them by adding the values in the numerators and keeping the denominator the same. To convert a fraction into a different denominator, you have to multiply the numerator and denominator by the same number (in order to keep the actual value the same). The easiest way to convert two fractions to the same denominator is to make each denominator the least common multiple of the two previous denominators. With all that out of the way, let's see that example:
3/9 + 2/6
The least common multiple between 9 and 6 is 18 (you can learn how to find LCMs by using the search box in the top of any Khan Academy screen, if you don't know already). So, we multiply each fraction to get 18
3/9 * 2/2 = 6/18
2/6 * 3/3 = 6/18
Now, you have two fractions with the same denominator, so you can add them as normal:
6/18 + 6/18 = (6 + 6) / 18 = 12/18 = 2/3
(Note: you could have made the problem lots easier by simplifying the fractions at the beginning into 1/3 and 1/3 and then just adding those, but that would defeat the purpose of learning how to add unlike denominators.)
• what happends if you have a improper fration • can you do 1/9 + 6/9 - 1/9 + 1/9? • I think of it this way:
(1/9 + 6/9) - (1/9 + 1/9)
= (7/9) - (2/9)
= 5/9
So the answer would be 5/9
I remember being taught the MDAS (Multiplication, Division, Addition, Subtraction) method (which tells you which operations you would do first in given equation). For the problem you posed, I added all terms that needed to be added then I moved on to tackle the terms that needed to be substracted....Hope this helped.
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I want to know how important is it? • i want 9 prime • notice that he was having trouble while doing this. why is that? what do yall think   