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Session 9, Part B:
Decimals and Percents
In This Part: Percent as Proportion | Percents as Fractions and Decimals | Percent Models
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As we've mentioned, percents can also be expressed as fractions and decimals. In this case, all three representations are used to indicate some part of a whole.
• | What percent and decimal are represented by the fraction 1/8?
Using cross-multiplication (that is, multiplying both sides of the equation first by 100 and then by 8), we get 1 • 100 = 8x, so x = (1 • 100) 8. One hundred divided by 8 is 12.5, so x = 12.5%, or 0.125 (i.e., 12.5/100).
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• | What fraction and decimal are represented by 35%?
You can use the same process as above, but in this case it is easier to remember the definition of percent. Thirty-five percent means 35 out of 100, which is the fraction 35/100 (which reduces to 7/20) and the decimal 0.35 (35 hundredths).
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• | What percent and fraction are represented by the decimal 1.8?
This decimal is 1 8/10, or 18/10:
Since the denominator of this fraction is 10, it's easiest just to multiply both the top and bottom by 10, which gives us 180/100, or 180%.
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Problem B4 |  |
What percent and decimal are represented by the fraction 1/200? |
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Problem B5 | |
What fraction and decimal are represented by 0.2%? |
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Problem B6 | |
What fraction and decimal are represented by 170%? |
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Problem B7 | |
What fraction and percent are represented by the decimal 0.004? |
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Knowing some fraction, decimal, and percent equivalents allows you to estimate the answers for percent problems or conversions. Some critical values are shown in the following table:
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Problem B8 | |
If you have $12,000, how would you use this table to compute 25%? |
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Problem B9 | |
Twenty percent of an 80-meter bridge has been built. Using fractions, calculate how many more meters remain to be completed. |
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