Estimating calculations

Sometimes it is a good idea to estimate the value of a calculation rather than work it out exactly. In this situation, round the numbers in the question before performing the calculation. Usually, numbers are rounded to one significant figure. The 'approximately equal to' sign, ≈, is used to show that values have been rounded.

Examples

Estimate the value of \(23 \times 67\).

Rounding to 1 significant figure gives: \(20 \times 70 = 1,400\)

Therefore: \(23 \times 67 \approx 1,400\)

Estimate: \(\frac{423 - 98}{16.4}\)

Rounding to 1 significant figure gives: \(\frac{400 - 100}{20} = \frac{300}{20} = \frac{30}{2} = 15\)

Therefore: \(\frac{423 - 98}{16.4} \approx 15\)

Question

Estimate the value of \((58.4 \div 2.79) - 9.8\).

Question

Estimate \(\frac{68.7 - 9.9}{2.77}\).

Limits of accuracy

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Approximation - AQAEstimating calculations