# 7 th Grade Math Ms. Richardson.  To write a percent as a fraction  You can write 16 percent as or 16%  Your turn now:  Write the percent as a fraction.

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7 th Grade Math Ms. Richardson

 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%

 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.

 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.

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

 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

 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

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

1. 2.

 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

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

 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

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

 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

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

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

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.

 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

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.

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

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?

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

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

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

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

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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