Estimating calculations - Higher tier - Approximate measurements - Intermediate & Higher tier – WJEC - GCSE Maths Revision - WJEC

Estimating calculations - Higher tier

Sometimes it is appropriate to approximate a calculation rather than work it out exactly. In this situation, round the numbers in the question before performing the calculation. Rounding to one significant figure is often the best approximate rounding to use. The sign for ‘approximately equal to’ is ≈.

Example one

Estimate \(23 \times 67\)

Rounding to one significant figure gives:

\(20 \times 70 = 1,400\)

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

Example two

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

Rounding to one significant figure gives:

\(\frac{400 - 100}{20} = \frac{300}{20} = \frac{30}{2} = 15\)

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

Question

Estimate \((58.4 \div 2.79) - 9.8\)

Question

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

Upper and lower bounds – Higher tier

Rounding to significant figures – Higher tier

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Approximate measurements - Intermediate & Higher tier – WJECEstimating calculations - Higher tier