1. Pre-Algebra 8-2 Finding Percents Warm Up Evaluate. 1.2. 3.4. 1 3 1 3 + 14 2 15 3 – 7 12 3 4 5 7 2 1 2 3 1 4  Pre-Algebra 8-1 Relating Decimals, Fractions, and Percents 4 5 2 14 5 or

2. Pre-Algebra 8-2 Finding Percents Learn to relate decimals, fractions, and percents & finding percents!

3. Pre-Algebra 8-2 Finding Percents Percents are ratios that compare a number to 100. Ratio Equivalent Ratio with Denominator of 100Percent 3 10 1 2 3 4 30 100 50 100 75 100 30% 50% 75%

4. Pre-Algebra 8-2 Finding Percents To convert a fraction to a decimal, divide the numerator by the denominator. 1 8 = 1 ÷ 8 = 0.125 To convert a decimal to a percent, multiply by 100 and insert the percent symbol. 0.125  100  12.5%

5. Pre-Algebra 8-2 Finding Percents Find the equivalent fraction, decimal, or percent for each value given on the circle graph. 0.15(100) = 15% 7 20 = 0.35 FractionDecimalPercent 0.15 35% 38% 3 20 15 100 = 7 20 35 100 = 19 50 38 100 = 19 50 = 0.38 3 25 = 0.12 0.12(100) = 12% 3 25

6. Pre-Algebra 8-2 Finding Percents Fractions/decimal/percents You need to know these by heart – so memorize them!

7. Pre-Algebra 8-2 Finding Percents reminder: % means “out of 100” 2 ways to solve % problems: 1)Write as an equation & solve 2)Write as a proportion & solve

8. Pre-Algebra 8-2 Finding Percents To write as an equation & solve –“of” always means multiplication –“is always means “equal to” What % of 270 is 90? X (270) = 90 270 x = 1/3 x = 33.33%

9. Pre-Algebra 8-2 Finding Percents Try this one What % of 150 is 30? X(150) = 30 X = 30/150 X = 1/5 X = 20%

10. Pre-Algebra 8-2 Finding Percents What percent of 220 is 88? Method 1: Set up an equation to find the percent. p  220 = 88. 88 220 p = p = 0.4 So 88 is 40% of 220.

11. Pre-Algebra 8-2 Finding Percents To solve as a proportion Number = part 100 whole What % of 270 is 90? # we are looking for whole part

12. Pre-Algebra 8-2 Finding Percents x = 90 100 270 Then cross multiply & solve for “x” X(270) = 90(100) 270x = 9000 X = 9000/270 X = 33.33%

13. Pre-Algebra 8-2 Finding Percents B. Eddie weighs 160 lb, and his bones weigh 24 lb. Find the percent of his weight that his bones are. = number 100 part whole Set up a proportion. Substitute. n 100 24 160 = n  160 = 100  24 160n = 2400 Find the cross products.

14. Pre-Algebra 8-2 Finding Percents n = 15 = 15 100 24 160 The proportion is reasonable. Solve for n. 160 2400 n = So 15% of Eddie’s weight is bone.

15. Pre-Algebra 8-2 Finding Percents B. Mr. Downing deposited $770 in the bank. Four years later her account held 120% of the original amount. How much money did Mr. Downing have in the bank at the end of the four years? method: Set up a proportion. = 120 100 a 770 Set up a proportion. 120  770 = 100  a Find the cross products. 92,400 = 100a

16. Pre-Algebra 8-2 Finding Percents Try This: Example 2B Continued 924 = a Solve for a. Mr. Downing had $924 in the bank at the end of the four years.

17. Pre-Algebra 8-2 Finding Percents Lesson Quiz Find each percent to the nearest tenth. 1. What percent of 33 is 22? 2. What percent of 300 is 120? 3. 18 is what percent of 25? 4. The volume of Lake Superior is 2900 mi 3 and the volume of Lake Erie is 116 mi 3. What percent of the volume of Lake Superior is the volume of Lake Erie? 40% 66.7% 72% 4%