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Chapter 6, Section 4: Proportions and Percents Warm Up: Solve each proportion = 98.9 d 43 100 X = 7 D = 230 K = 25 M = 18 = 25 100 x 28 = 52 100 13 k = m 100 27 150
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Percent Proportion <ul><li>Drawing a model can help solve percent problems. Like finding 75% of 40. </li></ul>0% 0 75% 30 40 100% Part Whole Draw a model of 0 to 40. Then divide the model into 4 sections and color in 3 of the 4 sections. You can also make a proportion. 75/100 = 30/40
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Example 1 <ul><li>Find 65% of 245. </li></ul>0% 0 100% 65% 245: Whole n part 65/100 = n/245 (Write a proportion) 65(245) = 100n (Cross Product) 65(245)/100 = n (Division Prop. Eq.) n = 159.25 159.25 is 65% of 245.
4.
Now, Do It Without Drawing <ul><li>25% of 124 is ____ </li></ul><ul><li>43% of 230 is ____ </li></ul><ul><li>12.5% of 80 is ____ </li></ul>31 98.9 10 IS OVER OF Turn the % into a fraction equal to IS over Of.
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What Percent of a # is #? <ul><li>Example: What Percent of 60 is 52? </li></ul><ul><li>Therefore, 52 is what Percentage of 60? </li></ul><ul><li>It’s the same process and set up, just make sure you know where your unknown goes!!! </li></ul>52/60 = x/100 (remember that percent is fraction with a denominator of 100). (cross product) (simplify) (solve)
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Determine Percentage, to 10 th of a Percent <ul><li>What percent of 250 is 138? </li></ul><ul><li>14 is what percent of 15? </li></ul>
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Finding Whole Amounts. <ul><li>When you know PERCENT that a part represents, and you want to FIND the WHOLE AMOUNT. </li></ul><ul><li>Our class fundraising committee might announce, “We’ve collected $207 so far, which is 46% of our goal!” </li></ul><ul><li>Use proportions to calculate the goal. </li></ul>
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Figure This One Out. <ul><li>207 is 46% of what number? </li></ul>
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Try These Too <ul><li>19 is 75% of what number? </li></ul><ul><li>310 is 99% of what number? </li></ul>25.3 313.1
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Word Problem <ul><li>In 1998, the number of drive-in movie screens in the United States was only about 21% of the number in 1980. About how many drive-in screens were there in 1980? </li></ul>3,560 Estimated 748 1998 915 1990 ? 1980 Number of Screens Year
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One More Drive In Question <ul><li>In 1990, the number of drive-in movie screens was about 32.4% of the number in 1985 (the year I was born). Find the number of drive-in screens in 1985. </li></ul>2,824 Screens 748 1998 915 1990 ? 1980 Number of Screens Year
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