Section 11.1, Percent

• Percent means "per hundred"
• It is the ratio of two numbers, multiplied by 100.
• Specifically it is parts/whole X 100
• It is a dimensionless way to compare things.
• You took two tests, on the first you scored 37 out of 58, on the second you scored 7 out of 10, on which test did you do better?

  The first test: 37/58 × 100 = 64%
  The second test:  7/10 × 100 = 70%
      

• To change a decimal to a percent:
  • Multiply the decimal by 100.
  • Add the % sign.
• To change a percent to a decimal:
  • Remove the % sign.
  • divide by 100.
• To change a fraction to a percent:
  • Divide numerator by denominator to obtain a decimal.
  • Convert the decimal to a percent as above.
• Express 1/5 as a percent
• Express 21/35 as a percent
• Express 0.0399 as a percent
• Express 0.0000123 as a percent
• Express 35% as a decimal
• Express 1/2% as a decimal
• Sue has 24 credits, she needs 64 credits, what percent of her degree is completed?
• 500 people took a survey about a movie. 37% did not like the movie. How many people did not like the movie?
• What is 12% of 30?
• What percent of 90 is 35?
• 54% of what number is 72?
• Percent Change
  • When we have two different values for something.
  • Percent Change = (new value - old value)/ old value × 100%
• A dress cost $700, but the price was lowered to $500. What is the percent decrease?