Activity 22: Magic FractionsFebruary 27, 2008 through March 5, 2008 |
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| ACTIVITY OVERVIEW In this activity we will:
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First of all, unit fractions are fractions whose numerator is 1. 1/2, 1/3, 1/6, 1/5, 1/9 are all unit fractions. |
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First, we need to set up the calculator so that it doesn’t automatically give us simplified answers or mixed numbers. Press the  key and set up your screen like the one on the right by arrowing to the highlighted setting and pressing  |
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Try this problem on your calculator. Add 1/2 and 1/3. To enter a fraction, type the numerator and then press the [b/c] key. Enter the denominator and then press the  key. Your screen should look like the one at the right before you press to do the addition. |
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| Press to get the answer. Record this entire problem in your notebook. Try this problem. 1/2 +1/5. Do you notice anything about |
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Do all of these problems and record the answers on the right. |
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Look at the numerator in the answer and the denominators in the problem. Look at the denominator in the answer and the denominator in the problem. Do you see a pattern? |
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| In the problem 1/8 + 1/3, the answer is 11/24. Notice that the answer in the numerator is 11 and the two denominators 8 and 3, add to 11. The denominator in the answer is 24 and the denominators in the problem, 8 and 3, multiply to 24. |
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Now you have a quick method to find answers for fraction problems with unit fractions. |
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Extension The calculator does not use this method for all problems. Try 1/2 + 1/6. What is the answer? Why is the denominator not 12? Why is the numerator 4 and not 8? What is different about this problem? |
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Can you come up with a method to subtract unit fractions? |
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