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WHAT PERCENT? Lesson 29 Section 2 We have seen: To change a number to a percent, multiply it by 100, and add the % sign. Example 1.
Example 2. 7 out of 12 people voted Yes. What percent voted Yes?
Write
"12 goes into 70 five (5) times (60) with 10 left over." (Lesson 11.) "12 goes into 100 eight (8) times (96) with 4 left over."
Always:
To do this problem with a calculator, press
See
This is approximately 58.3%. Division expresses the fraction as a decimal. (Lesson 23.) The % key multiplies it by 100. |
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Certain fractions come up frequently, and the student should know their percent equivalents. See Problem 17 at the end of the Lesson. Example 3. 15 is what percent of 20? Solution. Write the fraction
-- is 75%. 15 is 75% of 20. Equivalently, to ask 15 is what percent of 20? is the same as asking 15 has what ratio to 20? They have a common divisor 5. "5 goes into 15 three times. 5 goes into 20 four times." 15 is three fourths of 20. (Lesson 16, Question 7.)This means that 15 is 75% of 20. Really, this should be a mental calculation. Example 4. What percent of 27 is 18? Solution. The Base is 27 -- it follows "of." In standard form: 18 is what percent of 27? Now, 9 is a common divisor, and 9 goes into 18 two times, and into 27 three times.
Example 5. 20 is what percent of 8?
20 is 250% of 8. (2½ times 100% is 250%.) Example 6. .8 is what percent of 4?
terms by 10:
.8 is 20% of 4. Example 7. Calculator problem. 7 is what percent of 11?
(Lesson 13) See 63.63636364 On rounding off to one decimal place, this is approximately 63.6%
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