April 30, 2009

1. April 30, 2009 “Nobody can go back and start a new beginning, but anyone can start today and make a new ending.” ~Maria Robinson

2. Final Exam Tuesday, May 12 11am – 1pm In our usual classroom Cumulative (covers material from entire semester). As always, you may use a calculator and/or manipulatives from your own pack.

3. April 30, 2009 • Section 6.2 (finish) • Exploration 6.5 • If time – Exploration 6.7

4. 6.2 (cont’d) Fractions, decimals, percents To write fractions as decimals or percents: • a/b means a ÷ b. Divide, and write the answer to get the decimal. Then, multiply by 100 to get the percent. Ex:48/60 = 48 ÷ 60 = 0.8 = 80% You try: 4/9, 4 3/20

5. 6.2 (cont’d) Fractions, decimals, percents To write decimals as fractions or percents: • Consider using expanded form, then combine fractions and simplify. • To write a percent, multiply by 100. Ex: 0.09 = 9/100 = 9% You try: 7.007, 0.59

6. 6.2 (cont’d) Fractions, decimals, percents To write a percent as a decimal, divide by 100. • From there, you can convert the decimal to a fraction. Ex: 591% = 5.91 = 5 91/100 You try: 3%, 62%, 0.4%

7. 6.2 (cont’d) What happens if... What if you have 3 2/5% Rewrite 2/5 as 0.4. So 3 2/5% = 3.4%

8. 6.2 (cont’d) Ways to estimate: Ex: A newspaper story reports that 8% of 7968 students work full-time. • Strategy 1: Use 10% as a benchmark10% of 7968 is 796.8, or about 797. • Strategy 2: Use 1% as a benchmark1% of 7968 is 79.68, or about 80. So 8% is 8 • 1%: 8 • 80 = 640.

9. 6.2 (cont’d) Ways to estimate: A newspaper story reports that 8% of 7968 students work full-time. • Strategy 3: find a close number:7968 is about 8000:10% of 8000 is 800; 8 • 1% is 8 • 80 = 640. • Strategy 4: find a range. 8% is between 5% and 10%.5% of 8000 is 400. 10% of 8000 is 800. So 8% of 7968 is between 400 and 800.

10. 6.2 (cont’d) A newspaper story reports that 8% of 7968 students work full-time. For an exact answer: • Write and solve a proportion. Percent = part 100 whole 8 = x 8 • 7968 = 100x 100 7968 63744 = 100x 637.44 = xAbout 637 students work full time.

11. 6.2 (cont’d) Ex: Suzanne makes 68 baskets a week, and wants to sell at least 30%. What is the minimum number of baskets she can sell? Part = Percent Whole 100 30 = x 30 • 68 = 100x100 68 x = 20.4, so Suzanne should sell at least 21 baskets. (Why did I round up here?)

12. 6.2 (cont’d) You try: A child has 72 stuffed animals on his bed, but he generally only sleeps with 4 at a time. What percent of his animals does he sleep with?

13. 6.2 (cont’d) You try: A child has 72 stuffed animals on his bed, but he generally only sleeps with 4 at a time. What percent of his animals does he sleep with? 4 = x 4 • 100 = 72x. 72 100

14. 6.2 (cont’d) You try: There is a 20% off sale at the mall. I’ve wanted a particular sweater that is $120, but couldn’t afford it. How much less is the price with the sale? What is the sale price? Can you explain how to do this in your head?

15. 6.2 (cont’d) Answer: If the sale is 20% off, then the sweater is going to cost 100% – 20% = 80% of the original price. New price: $96. Savings: $24.

16. Exploration 6.5 Do the parts labeled “Sales” and “Percent Decrease and Increase”. This will be due Tuesday, 5/5.

17. 6.2 (cont’d) Ex: The college bookstore makes a profit by charging students 25% more than the book actually cost wholesale. If your book cost $140, how much did the bookstore pay for it?

18. 6.2 (cont’d) Answer: The bookstore pays 100%, and you pay 100% + 25% = 125%. 100% = $x 100 • 140 = 125x 125% $140 x = $112

19. 6.2 (cont’d) Ex: In the course of a year, there has been a decrease of 0.5% in the number of cacti in a certain zip code. If there had been about 640,000 cacti at the beginning of the year, how many are left now?

20. 6.2 (cont’d) Answer: 100% in the beginning; 100%  0.5% = 99.5% now. 100 = 640,000 100x = 99.5 • 640000 99.5 x About 636,800 cacti are left.

21. Homework Link to online homework list: http://math.arizona.edu/~varecka/302AhomeworkS09.htm *Note: approximate grades are posted on D2L.