page is designed to help you better understand how to deal with fractions and
their uses in Pre-Algebra. Click any of the links below to go to that section and start
Greatest Common Factor
Multiplication of fractions
Division of fractions
Quiz on Fractions
The LCM is something that you will use throughout math. It is especially useful when multiplying and dividing fractions.
This section will help you better understand the LCM and its uses.
4, 8, 43, 104
When finding LCMs, be aware of all the numbers you are finding common multiples of and remember that you can only use whole numbers for multipliers. Also, always be aware of zero, which is not an LCM.
Problem: Find the LCM of 4 and 5.
20 is a multiple of both numbers.
It is also the first one (lowest of all multiples), thereby being the lowest common multiple.
The GCF is something that you will use throughout your "math experience." It is especially useful when dealing with fractions.
This section will help you better understand how to find and deal with GCFs.
2, 9, 27, 201
When finding GCFs, be aware of all the numbers you are finding common factors of and remember that you can only use whole numbers for factors. When finding a GCF, unlike the LCM, you must list all the factors because you're finding a greatest factor, not a lowest multiple.
Problem: Find the GCF of 8 and 12.
4 is a factor of both numbers.
It is the largest of the factors listed, therefore it is the greatest common factor.
The multiplication of fractions is one of the more important things you'll learn in math. In fact, it is so important that you need to know how to do it in order to divide fractions, add fractions, and many other things.
This section will help you better understand the important skill of fraction multiplication.
1 3 4 12 3 - * - * - = -- = - 2 2 5 20 5
When multiplying fractions, multiply the numerator(s) by the numerator(s) and the denominator(s) by the denominator(s). Also, after finding the product of the fractions, be sure to reduce the product to its simplest form (that is one instance of GCF use).
Division of fractions isn't a skill that gets around quite as well as multiplication, but it is very useful!
This section will help you understand how to divide fractions.
1 3 2 4 2 20 5 - / - / - = - / - = -- = - 2 4 5 6 5 12 3
When dividing a fraction by a fraction (remember, a whole number can be written as a fraction (i.e., 4 = 4/1)), flip (take the reciprocal of) the second fraction and then multiply. Be sure to reduce the quotient (simplify the answer).
To be able to add or subtract fractions from fractions, you need to have the denominators be the same, or common. (This is one of many instances where the ability to multiply fractions correctly will come in handy.)
This section is designed to help you better understand the process involved in finding a common denominator in order to be able to add and/or subtract a fraction from another number.
1 3 4 3 - + - cannot be done, but - + - can. 2 8 8 8
2 - = 1 2
4 4 2 8 - = - * - = -- 5 5 2 10
When finding a common denominator so you can add or subtract fractions, you find the LCM of all denominators of the fractions you are dealing with. Once you've found this number, make the denominators equal this number. To do this, you multiply the denominator and numerator (the denominator is one factor of the LCM) by the corresponding factor of the LCM.
Take The Quiz on fractions. (Very useful to review or to see if you've really got this topic down.) Do it!