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# Cross Reducing

## on Sep 18, 2008

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## Cross ReducingPresentation Transcript

• A Shortcut Using Cross-Division to put our multiplication answers into simplest form quickly.
• Simplifying Fractions
• Start with a multiplication statement that looks like it will need to be simplified.
• Cross Reducing
• Normally, you would multiply the top numbers and then the top.
• Then check to see if your fraction is in simplest form.
• Cross Simplifying
• Now let’s look to see if we can cross reduce.
• First check the upper left and lower right corner.
• Is there any number that can divide evenly into 2 or 5?
Nope!
• Cross Simplifying
• Now let’s look to see if we can cross reduce the other pair.
• Check the upper right and lower left corners.
• Is there any number that can divide evenly into 3 or 3?
Yes! 3
• Let’s divide
• Since we can divide three into three at the top and do the same at the bottom, we do it right in the problem.
• Cross out
• Cross out the 3’s
• Divide the bottom left number by 3.
• Replace the three with a one.
• Divide the top right number by 3.
• Replace the three with a one.
1 1
• New Problem
• Multiply the top numbers.
• Multiply the bottom numbers.
• It will often be in simplest form after cross reducing and multiplying.
1 1
• Watch one
• Cross out the numbers divisible by 5.
• Divide the bottom left number by 5.
• Replace the five with a one.
• Divide the top right number by 5.
• Replace the ten with a two.
1 2
• New Problem
• Now proceed with the newly formed problem.
1 2
• Try these two.
• Try these two.
• Divide the 10 and 15 by 5
• Make the 6 a fraction.
• Divide the 2 and 6 by 2.
3 2 3 1
• Make a mixed number. 1 -2 1
• Work on Worksheet F4