1. Chapter 3 Approximation & Estimation

2. Learning Outcomes Round to nearest 10, 100, 1000 Round in practical problems Round to a specified number of decimal places Round to a specified number of significant figures Choosing a degree of accuracy for the answer that suits the question Estimating calculations

3. Rounding to nearest 10, 100,… If 5 or above round up If 5 or above round up If below 5 leave alone If below 5 leave alone Number Nearest 10 Nearest 100 Nearest 1000 7834 8323 20911 90892 9999

4. Practical Problems Remember to think if your answer is sensible!!!! Remember to think if your answer is sensible!!!! Example Example A year group are going on a trip to Paris. There are 242 students going. Each bus holds 55 passengers. How many buses are needed?

5. Rounding Decimals Start counting after the decimal place Start counting after the decimal place Number 1 dp 2 dp 3 dp 4 dp 2.7849 2.34535 0.0234 0.99999

6. Significant Figures Start counting at the 1 st non-zero digit Start counting at the 1 st non-zero digit Number 1 sf 2 sf 3 sf 4 sf 2.7849 234.535 0.0234 99.999

7. Choosing a Degree of Accuracy Use common sense!!! Use common sense!!! If answer is in metres use 2 dp If answer is in metres use 2 dp If a question is given to 1 dp the answer should be given to 1 dp If a question is given to 1 dp the answer should be given to 1 dp

8. Estimation When estimating a calculation use 1 significant figure or round to numbers that give even answers When estimating a calculation use 1 significant figure or round to numbers that give even answers Examples Examples 1) Estimate 432 × 29 2) Estimate (49.7 + 10.6) ÷ (9.69 × 3.04) 3) Estimate 78.9 ÷ (0.037 × 5.2)