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7 th Grade Math Ms. Richardson

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To write a percent as a fraction You can write 16 percent as or 16% Your turn now: Write the percent as a fraction in simplest form. 24%2. 55%3. 87%4. 12%

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To Write a fraction as a percent, rewrite the fraction with a denominator of 100. Example 1: Write as a percent. = 80% Your turn now: Write the fraction as a percent 5. 6. 7. 8.

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You can write a percent as a decimal and a decimal as a percent by using a fraction as an intermediate step. For example: 37% = = 37 ÷ 100 = 0.37 So, 37% = 0.37. Notice that 37% can be written as a decimal by dropping the percent sign and moving he decimal point two places to the left. A decimal can be written as percent by moving the decimal pint two places to the right and adding a percent sign.

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Writing percents as decimals A. 48% = B. 9% = C. 75.5% = Writing decimals as percents A. 0.13 = B. 0.04 = C. 0.027 =

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Write the percent as a decimal or decimal as percent. 1. 25% 2. 1% 3. 5.2% 4. 0.082 5. 0.06 6. 0.578

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To write a decimal as a fraction, use the place value of the last digit of the decimal to determine the denominator. For Example, to write 0.45 as a fraction, use the fact that 5 is in the hundredths’ place and write. Write the decimal as a fraction in simplest form. 1. 0.40 2. 0.735

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To write divide the numerator by the denominator. For example: Write as a decimal

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1. 2.

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A proportion is an equation that states that two ratios are equivalent. For Example: The proportion is read “3 is to 5 as 6 is to 10.” When one of the numbers in a proportion is unknown,, you can find the number by solving the proportion. You can solve the proportion by: Using equivalent ratios Using algebra Using cross products

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Example: A person burned about 150 calories while skateboarding for 30 minutes. About how many calories would the person burn while skateboarding for 50 minutes? You will use a proportions to answer this question To find the number C of calories the person would burn while skateboarding for 60 minute, solve the proportion

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1. Ask yourself:What number can you multiply 30 by to get 60? ×? 2. Because 30 × 2 = 60, multiply the numerator by 2 to find C. ×2 ×2

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Because 150 × 2 = 300, C = 300. So the person would burn about 300 Calories while skateboarding for 60 minutes.

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Solve the proportion 1 st Write the original proportion 2 nd Multiply each side by 25 3 rd Simplify 4 th Simplify the fraction The solution is 15

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In the proportion, the products of and are called cross products. Notice that the cross products are equal.

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Use the cross products property to solve 1st Write the original proportion 2 nd Cross Products Property 3 rd Divide each side by 2 4 th Simplify

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Use equivalent ratios to solve the proportion 1. 2. Use algebra to solve the proportion 3. 4. Use the Cross Product Property to solve the proportion 5.

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There are different ways to sep up a proportion. For Example: Yesterday you bought 8 bagels for $4. Today you want only $5 bagels. How much will 5 bagels cost? or It could never be

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Solve this problem by setting up a proportion Use all 3 methods to solve the proportion Example: At maximum speed, the elevators in the Empire State Building can pass 80 floors in 45 seconds. How many floors can the elevator pass in 9 seconds.

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We can solve problems involving percents by: Setting up a proportion Using decimals Using fractions

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The set up will always be the same “Is over of is equal to what percent over 100?” The proportion method will work for all 3 types of questions you may be asked 1. What is 75% of 4? 2. 3 is what percent of 4? 3. 75% of what number is 3?

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1 st Write the formula for the proportion 2 nd Fill in the information given in the problem 3 rd assign a variable for the unknown 4 th solve for the variable using one of the 3 ways to solve a proportion Equivalent ratios Algebra Cross product property

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What percent of 24 is 18? What Percen t Of 24 Is 18?

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What number is 30% of 120? What Numbe r is 30%Of 120?

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12 is 80% of what number? 12 is80% Of what Number ?

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1. What number is 76% of 25? 2. What percent of 40 is 16? 3. 18 is 45% of what number?

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