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Estimation and checking answers.

Learn how to estimate answers to mathematical calculations without a calculator. Practice rounding numbers to check if your calculated answers are sensible. Includes examples and tips for effective estimation strategies.

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Estimation and checking answers.

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  1. Estimation and checking answers.

  2. What you should already be able to do: • Round to the required number of decimal places. • Round to the required number of significant figures (especially to 1 sig. Fig.). • Recognise the square numbers up to 102 = 100. If you are not sure about any of these then visit the relevant section in the Moodle.

  3. What is estimation? • Estimation is a method to check if an answer you have calculated is sensible and therefore possibly correct. • You should ALWAYS do an estimation whenever you have worked out any calculation especially when using a calculator. • There could also be discrete estimation questions on your exam paper (if you calculate the exact answer for these it will be incorrect).

  4. How do we estimate? • To estimate we need to round the numbers so that we can work out the calculation without using a calculator. • This is usually done by rounding to 1 significant figure.

  5. Work out 7·3  4·8 Estimate: 7·3 is 7 to 1 sf. 4·8 is 5 to 1 sf. 7·3  4·8 is about 7  5 = 35 Calculation: 7·3  4·8 = 35·04 35 is near to 35·04 so the answer is probably right.

  6. Work out 84 29 Estimate: 84 is 80 to 1 sf. 29 is 30 to 1 sf. 84 29 is about 80  30 = 2400 Calculation: 84 29 = 2436 2400 is near to 2436 so the answer is probably right.

  7. Estimating Square Roots

  8. Exam Type Questions. Clearly showing how you obtained your answer, ESTIMATE the value of 132 is about 100 892 is about 900 285 is about 300

  9. Exam Type Questions. Clearly showing how you obtained your answer, ESTIMATE the value of 21·5 is about 20 89·3 is about 90 8·9 is about 9

  10. Exam Type Questions. Clearly showing how you obtained your answer, ESTIMATE the value of 212 is about 200 63 is about 60 319 is about 300

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