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Estimating Sums and Differences

Estimating Sums and Differences. Amanda Hobson. Objectives:. The students will: 1. Give the definition of Estimation. 2. Explain the differences in rounding and front-end estimation. 3. Estimate the sums or differences using the two methods. Estimation.

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Estimating Sums and Differences

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  1. Estimating Sums and Differences Amanda Hobson

  2. Objectives: The students will: 1. Give the definition of Estimation. 2. Explain the differences in rounding and front-end estimation. 3. Estimate the sums or differences using the two methods.

  3. Estimation Finding the value that is close enough to the right answer, usually with some thought or calculation.

  4. Estimation Methods: • Rounding • Front-End Estimation

  5. Rounding Rounding means reducing the digits in a number while trying to keep its value similar. The result is less accurate, but easier to use.

  6. Rounding Example: 73 rounded to the nearest ten is 70 because the 3 is less than 5; therefore the number 73 will be rounded down.

  7. How to Round Numbers • Decide which is the last digit to keep • Leave it the same if the next digit is less than 5 (this is called rounding down) • Increase it by 1 if the next digit is 5 or more (this is called rounding up)

  8. Estimate the Sum by Rounding Example: (round to the nearest ten) 26 + 14 26 30 + 14 + 10 40

  9. Estimate the Difference by Rounding Example: (round to the nearest thousand) 5,976 - 2,687 5,976 6,000 -2,687 - 3,000 3,000

  10. Front-End Estimation A method in which the front digits in the given numbers are added or subtracted

  11. Front-End Estimation Front end estimation mostly produces a closer estimate of sums or differences than the answer produced by adding or subtracting rounded numbers.

  12. How to estimate the sum using Front-End Estimation • Add the digits of the highest place values • Insert zeros for the other place values

  13. How to estimate the sum using Front-End Estimation Example: 44,859 + 25,789 44,859 40,000 + 25,789 + 20,000 60,000

  14. How to estimate the difference using Front-End Estimation • Subtract the digits of the highest place values • Insert zeros for the other place values

  15. How estimate the difference using Front-End Estimation Example: 57,658 - 24,125 57,658 50,000 - 24,125 - 20,000 30,000

  16. Estimate Differences Rounding Front-End Estimation Estimate 4,892-1,431 Subtract the values of the front digits. 4,892 4,000 1,431 - 1,000 3,000 • Estimate 86,017-35,572 Round to the nearest ten thousand. 86,017 90,000 -35,572 -40,000 50,000

  17. EstimateSums Rounding Front-End Estimation Estimate 4,254+2,415 Add the values of the front digits. 4,254 4,000 + 2,415 + 2,000 6,000 • Estimate 2,578+1,452 Round to the nearest thousand. 2,578 3,000 + 1,452 + 1,000 4,000

  18. Review: • What is estimation? • Estimation is the value that is close enough to the right answer. (Guess) • What is the difference in rounding and front-end estimation? • When you round , the result will be less accurate . • Will you be able to estimate using the two methods you have learned?http://www.aaamath.com/g4_73ax1.htm

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