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Lesson 10

Lesson 10. Estimation. Estimation. In real life, an exact answer is not always necessary. Sometimes an estimated answer is all you need. Rounding is often a good way to estimate an answer. Lets take a look.

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Lesson 10

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  1. Lesson 10 Estimation

  2. Estimation • In real life, an exact answer is not always necessary. Sometimes an estimated answer is all you need. • Rounding is often a good way to estimate an answer.

  3. Lets take a look • Last year, Kevin earned $204 per week at his job. This year, he got a raise of $27 per week. What is a good estimate of the percent increase in his weekly pay? • What would you estimate? • Lets find what is close to 204 and 27. • Now we can find the percent increase. • His weekly salary increased by ABOUT 15%.

  4. Next example • Joanna figures that she saves 27% on groceries when she shops at the Warehouse Store instead of at Pete’s Supermarket. Last Thursday, she spent $83 at Pete’s Supermarket. If she had shopped at the Warehouse Store, approximately how much money would she save? • What common fraction has a value close to 27%? Well, 27% is close to 25% which is ¼. • Round $83 to the nearest $10. • Now, ¼ of 80 is…. How much would she save?

  5. One more example • A rectangular plot of land has dimensions of 148 feet by 67 feet. Vince estimated the area of the plot of land by rounding the numbers and multiplying. Area=length x width = 150 x 70= 10,500 square feet. What is the percent error of his estimate? • Percent error? That is where we find the percentage of the difference between the correct answer and his answer. • Find the real area. Subtract from actual. Put your answer over the actual area of the plot.

  6. Try some on your own • On Monday, about 19% of the 495 students enrolled at a middle school went on a field trip. What is the best estimate of the number of student who went? • Alfredo has a spool with 26.87 centimeters of wire. About how many pieces of wire, if each is 2.85 centimeters, can he cut? • A rectangle is 8.95 centimeters long and 0.75 centimeters wide. Caryn estimates its area as 9 square centimeters. What is the percent error?

  7. You know the drill • Amy saves $196 each week and deposits it in the bank. • Estimate the total amount of money Amy will have saved at the end of 52 weeks. • Find the actual amount Amy will save by the end of the 52 weeks. • How accurate was your estimate? Make sure you use percent error in your explanation.

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