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## MAP Recommended Practice

### Course: MAP Recommended Practice>Unit 34

Lesson 16: Adding and subtracting mixed numbers with unlike denominators

# Subtracting mixed numbers: 7 6/9 - 3 2/5

We can subtract two mixed numbers, by converting them to improper fractions. First, multiply the whole number by the denominator and add the numerator to get the improper fraction. Find a common denominator and adjust the numerators accordingly. Subtract the two improper fractions, and simplify the result if possible. Finally, convert the improper fraction back to a mixed number if desired. Created by Sal Khan.

## Want to join the conversation?

• Why do we need to add and subtract fractions?
• Well, suppose your cooking, and you need, say, 2/3 of a cup of sugar. What if your only doing half of a recipe? You need to chop 2/3 in half. Or if your doing 2 times the recipe. You need to double 2/3. This is only one example, there are lots of others.
• If you have a whole number minus a fraction for example 3 - 2 2/3 how do you do this
• Think of the numbers as improper fractions. For ex: 9/3 - 8/3 = 1/3.
That way all you have to do is subtract the numerators.
• Why the minus sign for 3-2/5? I still don't get it.
• Do you know about negative numbers? If you, then please realize - 1 (or minus one) is also a -1 (negative one).
• this is hard I can't do some problems with this even though he explained it 😪😪😪😯😯😥😥 so can someone explain it much more simpilaier or easier to me?
• Okay, Error.

For example:

12 3/4 - 7 4/5 = ?

Here, find the LCM of both the denominators.

4 and 5's LCM is 20, so it should be 12 ?/20 - 7 ?/20.

Here, multiply both numerators by the number you multiplied the denominator to get to 20.

Since you multiplied 4 against 5, which is 20, multiply 3 against 5, the answer to which is 12 15/20.

Since you multiplied 5 against 4, which is 20, multiply 4 against 5, the answer to which is 7 16/20.

Now, subtract the numbers.

Here, you need to borrow 1 from 12.

Borrow it, and add 20/20 to 15. You now have 12 35/20. Subtract 7 16/20 from it.

12 35/20 - 7 16/20 = 5 19/20.

Voilá! You're done!

#QED

Hope this helps, Error.
• why is fractions so important?
• Fractions will become important when you get older. For example, if you are baking, you have to know what 1/2 is or 1/4.
• 46 1/3 - 8 7/12 =
• Note that 1/3 = 4/12.

So 46 1/3 - 8 7/12 = 46 4/12 - 8 7/12.

This becomes 46-8=38, but with 3/12 missing. So the answer is 37 9/12, which reduces to 37 3/4.

Have a blessed, wonderful day!
• hello i nee lots of help i dont know how to add fractions if anyone noews the answer can someone pleaes3e tell me sporry my kat is walkijg over ny jkeayboard so i cant ytype very well its quite an issue yes. sorry for speaking bad francais i am not familiar with argentina.
• Well first do 1/2+1/2 the denominator stays the same so add the 1+1 that’s 2 so the answer for that is 2/2 also known as a whole aka 1

1/3+1/5 to find a common denominator multiply the denominator that’s 15 so for 1/3 u multiply 3x5 to be 15 so u do 1x5 for the numerator for 1/5 you do 5x3 to be 15 so do 1x3 for numerator to find that. Add them up and u got your answer.

I hoped this helped srry if it’s late and long!
• when do we usually use the add and subtract fraction in real life?
😕😕😕
• In the previous lessons, you learned that a fraction is part of a whole. Fractions show how much you have of something, like 1/2 of a tank of gas or 1/3 of a cup of water. In real life, you might need to add or subtract fractions. For example, have you ever walked 1/2 of a mile to work and then walked another 1/2 mile back?
• What happens if the first number is negative and you are subtracting them? Do you have to do something different?