Percent: 10.1

• Percent is a ratio of some number to 100.
  • If you got 14 out of 18 questions right on a test you had 78%
  • If you got 2249 questions out of 2300 right on a test you had 98%
  • See, even though you missed more questions on the second test, you had a better "score" or percent correct.
• We use percents to compare quantities which otherwise might not be comparable.
• Sometimes we are given a decimal and we want to change this to a percent
  1. Multiply by 100
  2. Add %
• Page 570, 11-14
• Frequently we are given a fraction that we want to change to a percent
  1. Divide the numerator by the denominator to obtain a decimal number
  2. Multiply by 100
  3. Add %
• Page 570, questions 7-10
• Sometimes we are given a percent and we want to change that to a decimal
  1. Remove the %
  2. Divide by 100
• Page 570, 15 - 22
• Remember

•                     part
            percent =------ x 100%
  	           whole
  

• Page 570-571 problems 23-38
• Percent change is defined as

•                            current  - previous 
  	 percent change = --------------------
  	                       previous
  

• If it is positive, it is a percent increase
• If it is negative, it is a percent decrease
• Page 571, 39-42