Estimation and checking answers.. What you should already be able to do: Round to the required number of decimal places. Round to the required number.

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Presentation transcript:

Estimation and checking answers.

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 10 2 = 100. If you are not sure about any of these then visit the relevant section in the Moodle.

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).

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.

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.

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 = is near to 2436 so the answer is probably right.

Estimating Square Roots

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

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

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