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Percents and Proportional Reasoning. Percents, Fractions, and Decimals Finding a Percent of a Number Lessons 6.6 & 6.7. CCS : 6.RP.3 . .
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Percents and Proportional Reasoning Percents, Fractions, and Decimals Finding a Percent of a Number Lessons 6.6 & 6.7
CCS: 6.RP.3. • Find a percent of a quantity as a rate per 100 (e.g., 30% of a quantity means 30/100 times the quantity); solve problems involving finding the whole, given a part and the percent. • Use ratio and rate reasoning to solve real-world and mathematical problems
Objectives • Students will be able to: • Represent percents in different but related ways, such as a ratio, a fraction and a decimal • Use proportions to solve percentage problems • Use decimals to calculate daily transactions (finding sales tax or figuring tips on restaurant bills)
Vocabulary • A percent is a ratio that compares a number to 100. It means “per 100.” • 49 out of 100 is 49%.
Writing Percents as Decimals • Imagine a decimal point in the place of the percent sign, and move the decimal two spaces to the left (the same as dividing by 100). .26 26% 40% .40 .4 .07 7%
Writing Percents as Fractions • Place the percent in a fraction with a denominator of 100. • Simplify the fraction. 26% 26 13 100 50 75 3 75% 100 4
Writing Decimals as Percents • Move the decimal point two spaces to the right, and add a % symbol (this is the same as multiplying by 100). 34% 1 100% .34 19% .19 .125 12.5% 60% .6
Writing Fractions as Percents • Divide the numerator by the denominator to get a decimal. • Change the decimal to a percent by moving the decimal point to the right (multiply by 100). 6 0.24 24% 25
Video Time • Writing Percents as Fractions and Decimals
Finding a Percent of a Number Should we use decimals OR proportions (fractions) OR both???
Using a Proportion • Set up a proportion that uses the percent over 100. • Cross multiply to write an equation. • Solve the equation. To set up your proportion, think, “IS over OF equals PERCENT over 100.”
Example – What is 20% of 30? x 20 part = 30 100 whole 100x = 30(20) 100x = 600 100 100 x 6 =
Using a Decimal • Change the percent to a decimal. • Multiply that decimal by the number you are finding the percent of.
Example – What is 18% of 70? 18% = 0.18 0.18 x 70 = 12.6
Video Time! • Finding Percents of a Number • Using Proportions to find Percents of a Number
Homework Time!Reteaching 6.6 and 6.7 Handout Classwork Time! • Math at the Mall -practice percentages and finding the best deal while shopping at a virtual mall