2.9 PERCENTS I can solve percent problems using proportions or the percent equation.
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Transcript of 2.9 PERCENTS I can solve percent problems using proportions or the percent equation.
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2.9 PERCENTSI can solve percent problems using proportions or the percent equation.
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THE PERCENT PROPORTION
“a is p percent of b” In this proportion, b is the base and
a is a part of the base. So here is the proportion:
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USING PROPORTIONS
What percent of 50 is 25? Use a proportion.
Cross product So 2500 = 50p 50 = p 50%
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PRACTICE
What percent of 56 is 42? 75%
What percent of 90 is 54? 60%
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THE PERCENT EQUATION a = p% ∙ b Ex: what percent of 40 is 2.5? 2.5 = p% ∙ 40 Solve for p
0.0625 = p% 6.25% = p%
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PRACTICE
Using the percent equation, what percent of 30 is 18? 60%
What percent of 56 is 35 62.5%
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FINDING A PART
A dress shirt that normally costs $38.50 is on sale for 30% off. What is the sale price?
a = 30% ∙ 38.50 will tell you how much is taken off
Or you can use a = 70% ∙ 38.50 to tell what the price will be
$26.95
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FINDING A BASE
125% of what number is 17.5? 17.5 = 125% ∙ b 17.5 = 1.25 ∙ b
14 = b
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SIMPLE INTEREST FORMULA
Simple interest is a common application of percents.
I = interest P = the principal (what you started
with) r = the annual interest rate t = time in years
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EXAMPLE If you invest $50 at a simple
interest rate of 3.5% per year for 3 years, what is the amount of interest earned?
I = this is what we’re solving for P = 50 r = 3.5% = 0.035 t = 3 I = $5.25
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ASSIGNMENT
ODDS ONLY P.141 #9-29