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Cross Reducing

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Cross Reducing

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