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1-1 Using Estimation Strategies

1-1 Using Estimation Strategies. Do Now: Round the following to the place of the underlined digit: 8 2 ,729 4 49 24,1 0 6 3, 5 28. Quick Tour of the Room. New Vocabulary. Compatible numbers: numbers that are easy to compute mentally ≈ Symbol that indicates estimation. Rounding.

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1-1 Using Estimation Strategies

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  1. 1-1 Using Estimation Strategies Do Now: Round the following to the place of the underlined digit: 82,729 449 24,106 3,528

  2. Quick Tour of the Room

  3. New Vocabulary • Compatible numbers: numbers that are easy to compute mentally • ≈ Symbol that indicates estimation

  4. Rounding • The span of an eagle ray’s fin is 3.27 m. The span of her baby’s fin is 0.88m. Estimate the difference between the spans. Round to the nearest whole number before you find the difference. • 3.27−0.88≈3−1  Round to the nearest whole number ≈2 Subtract

  5. Estimate. • First round to the nearest whole number • 1.75+0.92 • 14.34−7.8 • 4.90×6.25 2+1=3 14−8=6 5×6=30

  6. Front End Estimation • Add the “front-end” digits, ignoring the decimals. • Estimate the decimals. • Add the decimal estimate to the front-end sum.

  7. Example 5.45 9.89 3.53 6.03 Front-end: 5 + 9 + 3 + 6 = 23 • Decimals: • .89 is close to 1. • .03 is close to 0. • .45 + .53 is close to 1. • 1 + 0 + 1 = 2 + About 25 Put the front-end with the decimal: 23 + 2 = 25.

  8. Compatible numbers go together! • Compatible • 54 and 9 • 16 and 4 • 32 and 8 • 12 and 3 • 54 and 6 • 18 and 2 • Not compatible • 17 and 2 • 35 and 9 • 15 and 4 • 27 and 8 • 24 and 5 • 15 and 6

  9. ESTIMATING Using Compatible Numbers • Overbidding 52 ÷ 6 overbid 52 count up: 53 no 54 yes 32 ÷ 5 overbid 32 count up: 33 no 34 no 35 yes 7 ÷ 4 overbid 7 count up: 8 yes Of course, you can use the multiples of the factor … multiplication facts.

  10. ESTIMATING Using Compatible Numbers • Underbidding 52 ÷ 6 underbid 52 count down: 51 no 50 no 49 no 48 yes 32 ÷ 5 underbid 32 count down: 31 no 30 yes 7 ÷ 4 underbid 7 count down: 6 no 5 no 4 yes Of course, you can use the multiples of the factor … multiplication facts.

  11. Compatible Numbers Underbidding Overbidding 20 17 ÷ 5 4 36 29 ÷ 9 4 48 42 ÷ 8 6 • 17 ÷ 5 3 15 • 29 ÷ 9 3 27 • 42 ÷ 8 5 40

  12. TRY THESE Use paper and pencil. Check on next page. • 73 ÷ 2 • 139 ÷ 2 • 236 ÷ 7 • 653 ÷ 9 Estimate • Did you overbid? • Did you underbid? • Did you change numbers to zero?

  13. Check your work! 80 40 140 70 73 ÷ 2 139 ÷ 2 70 35 120 60 280 40 720 80 236 ÷ 7 653 ÷ 9 210 30 630 70

  14. Minute Time! • Get ready, get set…

  15. Test Time • Number your paper 1-10

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