Homework Issues

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11/30

• Homework Issues
• 6.2
• Homework Due Monday 12/3 Assignment 16

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Homework Issues
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Assignment 13

• 30 Solve two different ways 3 ½ x 2 1/3. Why
  isnt the answer 6 1/6?

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• 48 ¼ off, 1/3 off, 1/2 off. Sale price is 12.
  What was the original price?

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Exploration 5.12

• Which of the following are fractions?
• 4, 4/5, 7/3, 8, 9/4
• Careful when you use the word numbers. When you
  add two numbers, is the sum always less than
  either original number?

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Exploration 6.4

• 4 cows, 3 weeks. 6 cows?

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6.2
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Percent

• Percent means per hundred.
• 50 means 50 per hundred, or 50/100.
• 2 means 2 per hundred, or 2/100.
• 315 means 315 per hundred, or 315/100

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Easy Percents--just know these

• 1 100
• 1/3 33.3, 2/3 66.6
• 1/4 25, 1/2 50, 3/4 75
• 1/5 20, 2/5 40, 3/5 60, 4/5 80
• 1/8 12.5, 3/8 37.5, 5/8 62.5, 7/8
  87.5
• 1/10 10, 2/10 20, etc..

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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.
• Example 48/60 48 60 0.8 80
• I am a personal fan of the move the decimal point
  over method.
• To turn .45 into a percent, multiply by 100, and
  move the decimal point two places over to the
  right.
• We see this decimal point moving when we use
  scientific notation.
• You try 4/9, 4 3/20

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Fractions, Decimals, Percents

• To write decimals as fractions or percents
• Read the decimal without the word point.
  Simplify if necessary.
• To write a percent, multiply by 100.
• Example 0.09 9/100 9
• You try 7.007, 0.59

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Fractions, Decimals, Percents

• To write a decimal from a percent, divide by 100.
• Move the decimal point to the left two.
• To write a fraction, read the decimal without the
  word point. Simplify if necessary.
• Example 591 5.91 5 91/100
• You try 3, 62, 0.4

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What happens if

• What if you have 3 2/5
• Rewrite 2/5 as 0.4. So 3 2/5 3.4

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Ways to estimate

• 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.

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Ways to estimate

• Strategy 3 find a close number7968 is about
  80001 of 8000 is ____
• What can we do then?
• Strategy 4 find a range.
• 8 is between 10 and 5.5 of 8000 is 400. 10
  of 8000 is 800. So 8 of 7968 is between 400 and
  800.

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For exact answer

• Write and solve a proportion.
• Percent part is 100 whole
  of
• 8 x --gt 8 7968 100x
• 100 7968 63744 100x
  637.44 xAbout 637 students work full time.

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For most problems

• Write the percent problem as a proportion then
  solve.

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Example

• My friend makes 68 baskets a week, and wants to
  sell no more than 30. What is the maximum
  number of baskets she can sell? Part
  Percent Is Whole 100 Of
• 30 x --gt 30 68 100x 100
  68
• About 20.

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Try this on your own

• My sister has 72 stuffed animals on her bed, but
  she generally only sleeps with 4 at a time. What
  percent of her animals does she sleep with?

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Example

• There is a 20 off sale at the mall. Ive wanted
  this really cool sweater that is 120, but
  couldnt afford it. How much is the discount
  amount? What is the sale price?

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Example

• 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?
• The bookstore pays 100, and you pay 100 25
  125.
• 100 x --gt 100 140 125x125
  140

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Example

• 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?

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Homework Due Monday 12/3