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The Percent Proportion. By Angela Gallacher 7 th Grade Mathematics James Workman Middle School. General Objective. NS 1.3 Convert fractions to decimals and percents and use these representation in computations, and applications.
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The Percent Proportion By Angela Gallacher 7th Grade Mathematics James Workman Middle School
General Objective NS 1.3 Convert fractions to decimals and percents and use these representation in computations, and applications. The student will solve problems proportions and percents, then explain to a partner how to solve a percent problem using proportions
Vocabulary In a percent proportion: • Percentage: The number that is compared to another number called the base. The ‘part’. • Base: The number to which the percentage is compared. The ‘total’ or ‘whole’. • Rate: The ratio of a number to 100. • Percent Proportion: P = R B 100
number part 100 = whole 66 n = 92 100 Method One: Finding the Percent One Number Is of Another What percent of 92 is 66? Set up a proportion to find the percent. Think:What number is to 100 as 66 is to 92? Set up a proportion. Substitute. n 92 = 100 66 Find the cross products. 92n = 6600 Simplify.
How to use a percent proportion: 40 is 20% of what number? Remember: P = R or is = % B 100 of 100 40 = 20 B 100 20b = 4000 20 20 b = 200
number part 100 = whole 21 n = 140 100 Solve using a proportion What percent of 140 is 21? Method 1: Set up a proportion. Think:What number is to 100 as 21 is to 140? Set up a proportion. Let n represent the percent. n 140 = 100 21 Find the cross products. 140n = 2100 Simplify.
= 21 140p 140 140 What percent of 140 is 21? Method 2: Set up an equation. percent whole = part Set up an equation. p 140 = 21 Let p represent the percent. Divide both sides by 140. p= 0.15 Simplify. 21 is 15% of 140.
= 22 33p 33 33 What percent of 33 is 22? percent whole = part Set up an equation. p 33 = 22 Let p represent the percent. Divide both sides by 140. p= 0.666666 . . Simplify. 22 is 66 2/3% of 33.
Practice • Write and solve a proportion for each. • What percent of 91 is 45? • What percent of 1270 is 375? • What percent of 240 is 180? • What percent of 186 is 75?
Think and Write • Show why 5% of a number is less than 1/10 of the number. • Demonstrate two ways to find 70% of a number. • Name fractions in simplest form that are the same as 40% and as 250%