1. Percents

2. Cent is Latin for 100 Century Cents in a dollar Centimeter Centennial Recall what ‘per’ means, tell the people at the table

3. per cents are rates Together ‘per cent’ means for every hundred The divisor is always a hundred 3/5 = 60/100 = 60% should not be a surprise to you

4. We will do percents as equivalent ratios (equivalent fractions ) Write the following in your notes, very large and clear and put a box around it. Part = % Whole 100 This is how you will set up each percent problem, as equivalent ratios

5. Sample percent problem Find 45% of 40 Notice that 45 is the percent and 40 is the whole Part = 45 40 100 simplify by using the common factor or 5 Part = 9 40 20 Clearly the Part must be 18 because 18 / 40 = 9 / 20 So the answer is 45% of 40 = 18

6. When Working The hard part is deciding which value is the part and which value is the whole. The percent is easy because it has a percent sign. Using this setup you can solve any percent problem. The problem will give two of the values for part or whole or percent. You will find the missing value. Be sure to set up the equivalent ratios each time

7. Another example Bill is downloading a file. It has taken 30 minutes to download 75% of the file. How long will the whole operation take? Is 30 minutes the part or the whole? What are we looking for? What is the percent?

8. Set up the equivalent ratio: Part / whole = % / 100 30 / whole = 75 / 100 Simplify 30 / whole = 3 / 4 The whole must equal 40, so the time needed to download the entire file will be 40 minutes.

9. Proportion A proportion is simply two equivalent ratios A nice way to check if the ratio are equal is ro use crossproducts. If the ratios are equal, the crossproducts are always equal Eg. Is 6 / 9 equal to 10 / 15 the cross products are the diagonal products. In this case, 6 x 15 and 9 x10 both of which equal 90. so the ratios must be equal.

10. Using crossproducts If 25% of the passenger seats on the bus are full and there are 56 seats on the bus, how many passengers are on the bus? Part / whole = % / 100 substitute in the values you know Part / 56 = 25 / 100 then 25 x 56 =part x 100 1400 = part x 100 Part =14

11. Classwork A and B’s do redbook do ch 7-9 page 382 # 3 to 8 (show the setup of the equivalent ratios each time), then do # 9, 10, 12 in 4 corners B/C’s do greenbook but you must show the setup of equivalent ratios with every question.pg 314 # 6 to 14. do word problems in 4 corners.