Estimating numerical calculations | Maths | Quizalize & Oak National Academy

Starter quiz

___________ figures are the digits in a number that contribute to the accuracy of the number. The first __________ figure is the first non-zero digit.
- Imperative
- Important
- Significant ✓
- Super important
- Vital
5689 rounded to 1 s.f. is ______.
- '6000' ✓
428.62 rounded to 1 s.f. is ______.
- '400' ✓
428.62 rounded to 2 s.f. is ______.
- '430' ✓
Sam correctly rounds an integer to the nearest 10. Sam's answer is 80. What could Sam's unrounded integer be?
- 78 ✓
- 91
- 94
- 75 ✓
- 84 ✓
Laura correctly rounds a number to 1 significant figure. Her answer is 8. What could Laura's unrounded number be?
- 8.457 ✓
- 8.547
- 7.849 ✓
- 7.584 ✓
- 7.458

Exit quiz

A quick ______ for a calculation is obtained from using approximate values, often rounded to 1 significant figure.
- guess
- number
- guess-timate
- estimate ✓
- round
Which of the following is the most accurate estimate calculation for 856 × 465?
- 900 × 500 ✓
- 1000 × 500
- 500 × 500
- 1000 × 1000
Which of the following are good, quick estimate calculations for 578 ÷ 1.785?
- 600 ÷ 2 ✓
- 580 ÷ 2 ✓
- 600 ÷ 1.8
- 578 ÷ 1.8
Which of the following are good, quick estimate calculations for ${4.56\times8.95} \over {7.65}$ ?
- ${5\times10} \over {10}$ ✓
- ${5\times10} \over {8}$ ✓
- ${5\times8} \over {8}$ ✓
- ${4.5\times9} \over {7.7}$
Which of the following are correct estimates for ${18.96\times2.15} \over {0.546}$ ?
- ${20\times2} \over {0.5}$ $= 20$
- ${20\times2} \over {0.5}$ $= 80$ ✓
- ${19\times2} \over {0.5}$ $= 19$
- ${19\times2} \over {0.5}$ $= 76$ ✓
Given Alex is of average secondary school pupil height. An estimate of the height of the elephant is ______ m. Give your answer to 1 decimal place.
- '3.0' ✓

Worksheet

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Lesson Details

Key learning points

All numbers can be rounded to a given number of significant figures.
Estimating gives you an idea of the size of an answer in context.
To estimate an answer you will often round to one significant figure.
Sometimes it makes sense to round to a different degree of accuracy when making an estimate.

Common misconception

Division by 0.5 is the same as doubling.

Reiterate the division of a number is the same as the multiplication of the reciprocal e.g The division of 0.5 is the same as multiplying by 2. e.g The division of 0.1 is the same as multiplying by 10.

Keywords

Estimate - A quick estimate for a calculation is obtained from using approximate values, often rounded to 1 significant figure.
Significant figures - Significant figures are the digits in a number that contribute to the accuracy of the number.