1. 1 EstimationStrategies Press Ctrl-A ©2009 – Not to be sold/Free to use Stage 5 Year 9

2. 2 End of Slide Estimation Strategies Estimation is important because we can check to see if our answer is correct. Sometimes because we only need an approximate answer. For example Bull Sharks off Port Macquarie.

3. 3 Estimation Strategies – Rounding  We can round numbers to estimate the answer. Round to 2345 to the nearest 1000 2345 + 7689 2000+ 80002000 8000 = 10,000 Round to 7689 to the nearest 1000 End of Slide

4. 4 x 800 Estimation Strategies – Rounding  We can round numbers to estimate the answer. Round to 12 to the nearest 10 12 x 789 10 800 ≈ 8,000 Round to 789 to the nearest 100 End of Slide

5. 5 B Estimate 27x99 A C D 27,0002703,000300 A B C D

6. 6 B Estimate 321+45 ADC 270300400370 A B C D

7. 7 2345 + 7689 2345 + 7689 2345 + 7689 Estimation Strategies – Front End 1  Use front-end numbers to estimate the answer. 2345 + 7689 Add 1 st column 2345 + 7689 9000 Add 2 nd column 900 + ≈ 9,900 End of Slide

8. 8 17.75 + 36.19 17.75 + 36.19 17.75 + 36.19 Estimation Strategies – Front End 2  Use front-end numbers to estimate the answer. 17.75 + 36.19 Add 1 st column 17.75 + 36.19 40.00 Add 2 nd column 13.00 + ≈ 53 End of Slide

9. 9 Estimation – Rounding & Front End Using both to estimate the answer. 228.45 – 76.89 RoundingFront End 228.45 – 76.89 230 – 80 228.45 – 76.89 150 228.45 – 76.89 150.00 223.45 – 76.89 228.45 – 76.89 2.00 + 152 Estimate from Rounding 150 Estimate from Front End 152 End of Slide Best Estimate

10. 10 Estimation Strategies – Clustering 1  We can cluster numbers & estimate the answer. 2345 + 7689 + 1650 + 2312 About 4,000 About 10,000 + ≈ 14,000 End of Slide

11. 11 Estimation Strategies – Clustering 2  We can cluster numbers & estimate the answer. 12.7 + 6.768 + 18.50 + 3.23 About 30 About 10 + ≈ 40 End of Show