April 30 2009 Nobody can go back and

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

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

April 30, 2009 • Section 6. 2 (finish) • Exploration 6. 5 • If time – Exploration 6. 7

$6. 2 (cont’d) Fractions, decimals, percents To write fractions as decimals or percents: •$

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

$6. 2 (cont’d) Fractions, decimals, percents To write decimals as fractions or percents: •$

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. 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%

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%

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 benchmark 10% of 7968 is 796. 8, or about 797. • Strategy 2: Use 1% as a benchmark 1% of 7968 is 79. 68, or about 80. So 8% is 8 • 1%: 8 • 80 = 640.

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.

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 = 100 x 100 7968 63744 = 100 x 637. 44 = x About 637 students work full time.

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 100 68 30 • 68 = 100 x x = 20. 4, so Suzanne should sell at least 21 baskets. (Why did I round up here? )

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?

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 = 72 x. 72 100

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?

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.

Exploration 6. 5 Do the parts labeled “Sales” and “Percent Decrease and Increase”. This will be due Tuesday, 5/5.

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?

6. 2 (cont’d) Answer: The bookstore pays 100%, and you pay 100% + 25% = 125%. 100% = $x 125% $140 x = $112 100 • 140 = 125 x

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?