Introduction: Multiplying Fractions

So you need to know how to multiply with fractions, huh? Well look no further than this Instructable! Here you can see how to multiply not only fractions, but also mixed numbers! Here goes nothing!

Step 1: Make It a Fraction ( for Mixed Numbers Only )

So, what is a mixed number? It is simply a number that has a whole part, and a part of a whole, such as one and one seventh, three and three fourths, etc. Also you should know that the numerator is the top number in a fraction, and the denominator is the bottom one. To convert the mixed number into a fraction, multiply the whole number by the denominator, then add this number to the numerator. This is your new numerator, and your denominator stays the same.

As an example, we'll use three fourths times one and one seventh. ( 3/4 ) * ( 1 1/7 )

Step 2: Cross-Reducing

This part will make your life much easier. Now, you should cross-reduce. To cross-reduce, you must rewrite the two fractions like picture 1. Then you draw imaginary lines diagonally and if either of the two sets of numbers have a common factor over one, you can divide both of them by the greatest factor. To find the greatest common factor, or GCF, you can either use your own way, or make factor rainbows, like picture 3. Make sure you have the GREATEST common factor, or else you will have to divide again. Now for the multiplication.

For our problem, the four and the eight have common factors, and the greatest common factor is four.

Step 3: The Multiplication

Now that you have reduced your fractions, all you have to do is rewrite them, and multiply across! You will probably be left with some big numbers, so to simplify, you first want to see if the numerator is higher than the denominator. If it is, then you want to see how many times the denominator can go into the numerator. The number you get is the new whole number, and the remainder is your new numerator. If, after multiplying, your numerator is smaller then your denominator, you can skip that. Now, like in step 2, you must divide by the GCF of the numerator and denominator if it is over one. The resulting quotients are the new numerator and denominator of the ending fraction.

After division, our problem is three wholes times two sevenths. Now, after multiplying, the answer to our problem is six sevenths. Since the GCF of six and seven is one, six sevenths is the final answer!!

Congrats! You can now multiply mixed numbers and fractions!

Comments

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MROHM (author)2010-12-15

VERY HELPFUL COLUMN !!!! MANY THANKS!!!

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