Question 600169: It has been a while that I have done fractions. I'm trying to help my son do his 4th grade homework.
Here is the problem. 8 2/7 - 5 5/7=
There is similar problems like that but I want to get a general idea on how to work them all step by step to help him with the rest.
Found 2 solutions by Alan3354, solver91311:
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! 8 2/7 - 5 5/7=
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Change to improper fractions.
8 2/7 = 58/7
5 5/7 = 40/7
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58/7 - 40/7 = 18/7
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Change to mixed number, or not.
18/7 = 2 4/7
Mixed numbers are not good for much.
Answer by solver91311(24713)  (Show Source):
You can put this solution on YOUR website!
If the fractions in each problem have the same denominator as in your example, proceed as follows:
Convert each of your mixed numbers into an improper fraction. A mixed number is a number that has a whole number part and a fraction part like in your example. An improper fraction is a fraction where the numerator (the top number) is larger than the denominator (the bottom number).
For each mixed number: Multiply the denominator of the fraction part times the whole number part. Add the numerator of the fraction part. This becomes the numerator of your improper fraction. The denominator of your improper fraction is the same as the denominator of the fraction part of the mixed number.
That is: for the mixed number  . Multiply 7 times 8 giving you 56. Add 2 giving you 58. 58 is then the numerator of your improper fraction. 7 is the denominator of the fractional part of the mixed number, so 7 is the denominator of the improper fraction, hence 
Using the same process you should be able to verify that  .
Now put the improper fractions back into the original problem:
When you add two fractions that have the same denominator, just add the numerators and keep the same denominator:
In algebra, I would leave the answer as an improper fraction.  of the time you want an improper fraction instead of a mixed number]. But 4th grade arithmetic may be a different story; just in case you need to do so, here is how to get back to a mixed number from an improper fraction.
Recall the old integer division process. That's how you originally learned division where the answer was a quotient and a remainder. Start with your mixed number. The quotient of the numerator divided by the denominator is the whole number part of the mixed number. The remainder is the numerator of the fractional part, and the denominator is the denominator.
7 goes into 18 2 times with a remainder of 4, hence:
If you have problems where the denominators are different, you need to calculate the lowest common denominator. That's a subject for another day.
A couple of things to note:
First, why did I mention addition when this is a subtraction problem? Save yourself some grief later on when you start working with signed numbers. Forget that there ever was a "subtraction" process. Always add. That is to say even though
and
)
are utterly equivalent statements, always think of the situation the second way.
Second, there is nothing "improper" or wrong about improper fractions. It is just a name used to distinguish fractions where the numerator is greater than or equal to the denominator from those fractions, called "proper" fractions, where the numerator is strictly less than the denominator.
John
My calculator said it, I believe it, that settles it
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