11.1 Percent

• Percent is parts per hundred.
• This gives us a way to compare different quantities.
  • Is $1.34 off a good thing?
    • Yes if we are talking about hamburgers
    • 1.34/3.99 &asympt; 34%
    • No if we are talking about new trucks.
    • 1.34/21000 &asympt; 0.0006%
• Percent is also part per whole.
  • part / whole * 100 = percent %
• They give three procedures:
  1. To change a fraction to percent
     • Divide the numerator by the denominator to obtain a decimal number
     • Multiply by 100
     • Add a percent sign.
  2. To Change a decimal number to a percent.
     • Multiply the decimal number by 100
     • Add a percent sign.
  3. To Change a percent to a decimal number.
     • Divide by 100
     • Remove the percent sign
• Examples:
  • Change the number to a percent.
    • 7/10
    • 11/20
    • 0.5688
    • 3.92
  • Change the percent to a decimal
    • 7%
    • 1/2%
    • 0.34%
• part/whole = percent
  • If you know two of these you can find the third.
  • Page 607 Problem 25
  • Problem 47, 49 and 51 page 609
  • But sometimes questions are a little tricky...
  • Problem 27 page 607
  • Problem 57 page 610
• Percent Change
  • Measures how much something has changed over a period of time.
  • percent change = (new value - old value)/old value x 100
  • Question 42 page 608
    • The answer was positive, so this means the population increased
    • Or a percent increase
  • Question 41 page 608
    • The answer was negative so this means the population decreased
    • Or a percent decrease.