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Estimating Percents

Estimating Percents. Section 7.3. Getting Started… 7.3 – estimating percents. What is 12.5% of 20? The enrollment at Booker T. Washington High School is 3800. If 65% of the students are not freshmen, how many students are in the freshman class? What is 40% of 999,990?. 2.5. 3800 * .35 =.

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Estimating Percents

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  1. Estimating Percents Section 7.3

  2. Getting Started…7.3 – estimating percents • What is 12.5% of 20? • The enrollment at Booker T. Washington High School is 3800. If 65% of the students are not freshmen, how many students are in the freshman class? • What is 40% of 999,990? 2.5 3800 * .35 = 1,330 399,996

  3. Estimating in Real Life • http://player.discoveryeducation.com/index.cfm?guidAssetId=13258913-21ac-4727-87ec-960ab3f5a214&productcode=HUB&CFID=266172&CFTOKEN=67708575

  4. Multiples of 1% and 10% • When you multiply a number by 1%, you move the decimal point two places to the left. example: 679 * 1% = 6.79 • When you multiply a number by 10%, you move the decimal point one place to the left. example: 679 * 10% = 67.9

  5. Find 11% of 26? • Break it down! (10 % + 1 % ) * 26 (10 % * 26 ) + (1 % * 26) 2.6 + .26 2.86

  6. Try one! • Find 80% of 25 (8 * 10 % ) * 25 8 * 2.5 20

  7. Comparable Numbers / Equivalent Fractions • Estimate 52% of 176? 52  .5  ½ 176  180 ½ * 180 = 90

  8. You try! • Estimate 72.5% of 258 ? 72.5 %  75%  ¾ 258  260 ¾ * 260 195

  9. Word Problem! • There are 48 cars in the faculty parking lot at Tom's school.19 of them are silver.  About what percent of the cars are silver? ≈ 20/50 ≈40% Actual: 39.58%

  10. You try: • Mid Valley High School reserves 35% of its parking so that each senior has a space. There are 626 parking spaces. Estimate the number of spaces reserved for seniors. 1/3 ≈ 35% ≈ 630 * 1/3 ≈ 210

  11. Homework • Extra Practice 7.3

  12. Another example: • Use mental math to estimate 15% of $48.60 • Use the distributive property: (10% + 5%) ($48.60) (10% * $48.60) + (5% + $48.60) ($4.86) + ($4.86/2) $4.86 + $2.43 $7.29

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