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7.2 Percentages:

You can represent “ a is p percent of b ” using the percent proportion:. 7.2 Percentages:.  =. =. Ex: what percent of 56 is 42?. =  =. cross multiply  56(x) = 100(42). divide by 56  x = 4200/56. =.  =. Ex: 125% of what number is 17.5?.

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7.2 Percentages:

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  1. You can represent “ a is p percent of b” using the percent proportion: 7.2 Percentages:  = = Ex: what percent of 56 is 42? =  = cross multiply  56(x) = 100(42) divide by 56  x = 4200/56

  2. =  = Ex: 125% of what number is 17.5? =  = cross multiply 125(x) = 100(17.5) divide by 125  x = 1750/125

  3. =  = Ex: A family sells a car to a dealership for 60% less than they paid for it. They paid $9000? For the car. What was the price they sold it the car for? =  = cross multiply 60(9000) = 100(x) divide by 100  x = 540000/100

  4. CLASSWORK:Page 141-142 Problems: 9, 14, 17, 21, 23, 29, 47, 49

  5. Percent change is the ratio of the amount of change to the original amount: 2.10 Change Expressed as Percent: Percent Change: Amount of Increase: new amount – original amount Amount of decrease: original amount – new amount

  6. The average monthly precipitation of Chicago, Illinois, peaks in June at 4.1 in. The average monthly precipitation in December is 2.8 in. What is the percent decrease from June to December? Percent Change: Percent Change: Percent Change: = 0.317 = 32%

  7. In one year the toll for the passenger cars to use a tunnel rose from $3 to $3.50.What was the percent increase? Percent Change: Percent Change: Percent Change: = 0.166 = 17%

  8. RELATIVE ERROR: PERCENT ERROR: relative error in percent You think that the distance between your house and a friend’s house is 5.5 mi. The actual distance is 4.75 mi. What is the percent error in your estimation?

  9. RELATIVE ERROR: You think that the distance between your house and a friend’s house is 5.5 mi. The actual distance is 4.75 mi. What is the percent error in your estimation? RELATIVE ERROR: = 0.157 = 16%

  10. CLASS WORK: Pages: 148-149 Problems: 7, 17, 19, 28

  11. MAXIMUM & MINIMUM:The most any measurement can be off by is one half of the unit used in measuring. Ex: A student’s height is measured as 66 in. to the nearest in. What are the student’s maximum and minimum possible heights? Maximum: (half of the unit more) Since the height is 66 in. and we are using inches, then maximum is .5 in more.  66in. + 0.5 in.= 66.5 in Minimum: (half of the unit less) Since the height is 66 in. and we are using inches, then maximum is .5 in less.  66in. - 0.5 in.= 65.5 in.

  12. MAXIMUM & MINIMUM:The most any measurement can be off by is one half of the unit used in measuring Ex: An ostrich egg has a mass of 1.1 kg. to the nearest tenth of a kg. Find the minimum and maximum possible measurements. Maximum: (half of the unit more) Since the mass is 1.1 kg and and we are using decimal, then maximum is .05 more since ½ of 0.1 is 0.05  1.1 kg. + 0.05 kg= 1.15 kg. Minimum: (half of the unit less) Since the mass is 1.1 kg and and we are using decimal, then minimum is .05 less since ½ of 0.1 is 0.05  1.1 kg. - 0.05 kg= 1.05 kg.

  13. CLASS WORK: Pages: Homework Problem: Finish the homework problems

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