Ch 3 Practice Problems: Percents Pg 59

Copyright © 2007 by Mosby, Inc. Test review What number has the greatest value? 0.004, 0.45, 0.8, 0.86 What number has the least value? 1.202, 1.22, 1.2, 1.222 Change the following decimal to a fraction 0.006 2/3 + 4/9 = 3 ½ x 1/8 = Copyright © 2007 by Mosby, Inc. All rights reserved.

Chapter 3 Percents

Copyright © 2007 by Mosby, Inc. Objectives Changing a fractions or decimals to a percent and percent to decimals Finding what percent one number is of another Finding the given percent of a number Copyright © 2007 by Mosby, Inc. All rights reserved.

Copyright © 2007 by Mosby, Inc. Percents page 53 A percent indicates a value equal to the number of hundredths. 96% =   96/100 9% = 9/100 77% = 77/100 What is a percent? A percent is another way of showing a fractional relationship. Fractions, decimals, and percents all can be converted from one form to the others. Copyright © 2007 by Mosby, Inc. All rights reserved.

Changing a Fraction to a Percent page 53 How can I change 4/5 to a percent? Multiply by 100. 4/5 × 100 is 80. Then add the percent sign to get the final answer, 80%. What is the equivalent percentage of 4/5? To determine the equivalent percentage, multiply by 100. In this case, 4/5 × 100 is 80. Then add the percent sign to get the final answer, 80%. Copyright © 2007 by Mosby, Inc. All rights reserved.

Changing a Decimal to a Percent Page 54 Multiply by the decimal number by 100. Or move your decimal two places to the right. Add the percent sign (%). Express 0.421 as a percent 0.421 x 100 = 42.1% Copyright © 2007 by Mosby, Inc. All rights reserved.

Changing a Percent to a Fraction page 54 How is a percent written as a fraction? Drop the % sign. Write the remaining number as the numerator. The denominator is always 100. 45% = 45/100 then reduce to lowest terms 9/20 How is a percent written as a fraction? The number with the percent sign becomes the numerator. The denominator is always 100. Copyright © 2007 by Mosby, Inc. All rights reserved.

Changing a Percent to a Fraction page 54 Example: 92% Drop the percent sign. Write the number as the numerator with 100 as the denominator. 92/100 Reduce to lowest terms, which is 23/25. What fraction is equal to 92%? Drop the percent sign. Write the number as the numerator with 100 as the denominator, which in this example is 92/100. Reduce to lowest terms, which is 23/25. Copyright © 2007 by Mosby, Inc. All rights reserved.

Changing a Percent to a Decimal page 55 How is a percent changed to a decimal? Drop the % sign. Divide the remaining number by 100. Dividing by 100 can be done by moving the decimal point two places to the left or you can use your calculator. Express the quotient as a decimal. 32% = 0.32 How is a percent changed to a decimal? Drop the percent sign, divide by 100, and express the quotient as a decimal. Dividing by 100 can be accomplished by moving the decimal point two places to the left. Change 45% to a decimal. Drop the percent sign, then divide by 100, and express the quotient as a decimal. 45 divided by 100 equals 0.45. Remember to place a zero before the decimal if there are no whole numbers. Copyright © 2007 by Mosby, Inc. All rights reserved.

Changing a Percent Containing a Fraction to a Decimal page 55 How is a percent containing a fraction changed to a decimal? Drop the percent sign. Change the mixed number to an improper fraction. Divide by 100. Reduce to lowest terms. Divide the numerator by the denominator, expressing the quotient as a decimal How is a percent containing a fraction changed to a decimal? First change the mixed number to an improper fraction. Multiply the denominator of the fraction by the whole number, then add the product to the numerator of the fraction. The sum is then placed over the denominator. What is the denominator of all whole numbers? The denominator of all whole numbers is 1. Copyright © 2007 by Mosby, Inc. All rights reserved.

Changing a Percent Containing a Fraction to a Decimal page 55 Example: 17 % Drop the percent sign, then change the mixed number to an improper fraction. In this example, 17½ is changed to 35/2. Divide the improper fraction by 100 and reduce to lowest terms. Divide the numerator by the denominator. The final answer is 0.175. Change 17½% to a decimal. Drop the percent sign, then change the mixed number to an improper fraction. In this example, 17½ is changed to 35/2. Divide the improper fraction by 100 and reduce to lowest terms. Divide the numerator by the denominator. The final answer is 0.175. Copyright © 2007 by Mosby, Inc. All rights reserved.

Copyright © 2007 by Mosby, Inc. All rights reserved.

Copyright © 2007 by Mosby, Inc. Bell Work 1/22 Change the following to a proper fraction reduced to lowest terms. 3/4% 24.8% Copyright © 2007 by Mosby, Inc. All rights reserved.

Finding Percentages of Numbers What percent of 24 is 9? Remember this equation is/of = x%/100 9/24 = x%/100 X= 37.5% Write the number after the word of as the denominator. Write the other number as the numerator. Divide the numerator by the denominator How is the word of used in finding what percent one number is of another? The number after the word of is used as the denominator of the fraction. How many places to the right of the decimal point should the decimal fraction be extended? The decimal fraction should be extended four places to the right of the decimal point. Copyright © 2007 by Mosby, Inc. All rights reserved.

Finding Percentages of Numbers Example 2: What percent of 6 is 2? 2/6 = x%/100 X= 33.3% What percent of 6 is 2? Write the number after the word of as the denominator and the other number as the numerator (in this example, 2/6). Divide the numerator by the denominator (0.3333). Multiply the decimal fraction by 100 and add the percent sign to get the answer (33.33%). Copyright © 2007 by Mosby, Inc. All rights reserved.

Finding Percentages of Numbers (cont’d) Example 3: What percent of 31 is 3 ? 3 ½ /31 = x%/100 X= 11.29% Divide the numerator by the denominator gives 3.5/31 (0.1129). Multiply the decimal fraction by 100 and add the percent sign to get the answer (11.29%). What percent of 31 is 3 1/2? In this example, dividing the numerator by the denominator gives 3.5/31 (0.1129). Multiply the decimal fraction by 100 and add the percent sign to get the answer (11.29%). Copyright © 2007 by Mosby, Inc. All rights reserved.

Finding the Given Percent of a Number Write the percent as a decimal number. Multiply by the other number. Example: What is % of 29? The decimal number would be 0.0080. Then multiply by the other number: 0.0080 × 29 = 0.232. What is 4/5% of 29? Write the percent as a decimal number. In this example, the decimal number would be 0.0080. Then multiply by the other number: 0.0080 × 29 = 0.232. Copyright © 2007 by Mosby, Inc. All rights reserved.

Copyright © 2007 by Mosby, Inc. All rights reserved.