Adding Fractions

Date: 7/26/96 at 21:40:8
From: Anonymous
Subject: Adding Fractions

How do you add fractions?

Date: 7/26/96 at 23:30:53
From: Doctor Paul
Subject: Re: Adding Fractions

There are two cases:

Case One:

You have the same denominator (the number on bottom) for both 
fractions.

Example:

3   1
- + - = ?
7   7


To do a problem where the bottom number is the same, just add the top
numbers and put that total over the common denominator.

So,

3   1    4
- + - =  -
7   7    7


Case Two:

To add fractions where the bottom numbers are different, we first put 
the fractions over a common denominator and then add using the 
previous method.

Example:

2   1 
- + - = ?
7   2

We have to put each term over the same denominator.  Note that if I 
multiply that top *AND* the bottom of a fraction by a number the 
fraction's value doesn't change.  I will multiply the 2/7 term by some 
number (a/a).  How do I choose 'a'?  I choose a to be the other 
denominator. I do the same to the 1/2 term: multiply it by (7/7)

so we get:

2 * (2)    1 * (7)
------- +  ------- 
7 * (2)    2 * (7)



  4       7        11
----  + ---- =    ---- 
 14      14        14

I hope this helps.

-Doctor Paul,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/