SUBTRACTION: Problem 2

Rule 19:

To subtract, the denominators must be equal. You essentially following the same steps as in addition.

1.: Build each fraction so that both denominators are equal.
2.: Combine the numerators according to the operation of subtraction or additions.
3.: The denominators will be the denominator of the built-up fractions.
4.: Reduce the answer.

Problem 2:

Calculate

and reduce your answer.

Answer:

The answer is

Solution:

The denominators are different, so you must build each fraction to a form where they both have the same denominator. Since 5 divides into 15 evenly, you only have to build the fraction

to an equivalent fraction with a denominator of 15. tex2html_wrap_inline62

can now be written tex2html_wrap_inline66

.
Combine the numerators for the numerator in the answer:

4 - 9 = -5.
The answer is tex2html_wrap_inline72 .
This fraction now needs to be reduced. tex2html_wrap_inline74

Check:

Now prove to yourself with your calculator that your answer is correct. Calculate 4 divided by 15, calculate 3 divided by 5, and combine the results. Now divide -1 by 3. Both answers should be the same. If you are correct, the answers are the same (equivalent) and you have successfully combine two fractions using subtraction.

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Author:Nancy Marcus