### Skills : Fractions 2

Saturday, April 25, 2009
In math class, we talked about subtracting fractions. To be able to subtract fractions, it has to have the same denominators. To get the same denominator you look for the lowest common denominator for example: 1/4 - 1/8, you can't subtract that because the denominators are different so you have to look for the lowest common denominator which is 8, you need to change 1/4 so the numerator is 2 and the denominator is 8. 2/8 - 1/8, is much better and you can now subtract. Mr. Harbeck also taught us how to subtract mixed fractions using two very effective techniques.

The first one is: turning it into an improper fraction, denominator x whole number + numerator = improper fraction. For example: 2 1/2 - 1 3/4 = ?, if you change it, it will be like this: 2 2/4 - 1 3/4. You can subtract 2 and 1 but you can't subtract 2 and 1 so you have to change it into an improper fraction: 10/4 - 7/4 = 3/4

The second one is: the borrowing technique, we use this when the numerator is too big. For example: 625 1/2 - 100 3/4 = ? or as an improper fraction: 1251/2 - 403 = ?, isn't that a bit more complicated? But, if you just borrow like this: ( 624 4/4 + 2/4) - 100 3/4 = ?, is much better because all you have to do is this:

Add 624 4/4 and 2/4 and the answer is 624 6/4. Then, you subtract 624 6/4 and 100 3/4 and the answer is 524 3/4.

Now, subtracting fractions are much easier whether it's improper, proper or mixed. (: