A quick estimate for a calculation is obtained from using approximate values, often rounded to 1 significant figure.

Significant figures are the digits in a number that contribute to the accuracy of the number.

Estimating numerical calculations

Maths

Checking understanding of rounding

Securing understanding of rounding

Rounding to three decimal places

Rounding to any number of decimal places

Rounding integers to one significant figure

Rounding integers to significant figures

Rounding decimals to significant figures

Degrees of accuracy

Checking by estimating

Truncating

Overestimating vs underestimating

Rounding errors

Inequality notation to express error

Using inequality notation for errors in calculations

Problem solving with estimation and rounding

In this unit, pupils have learnt how to round to a given number of decimal places or significant figures and explored the effect of using rounded numbers for calculations. In the future unit, pupils will investigate the bounds and perform calculations to determine a best/worst case scenario.

The prior unit on place value allowed pupils to develop the skills needed to estimate and round values. By understanding the value of each digit, pupils can determine what other values are close to the original value. This unit continues the exploration of the infinite nature of sets of numbers.

This unit helps pupils understand rounding to different decimal places, and significant figures. Pupils will also learn how to truncate numbers and understand the contexts in which these skills are useful. The unit ends will an exploration of rounding and inequality errors.

Estimation and rounding

A quick {{ }} for a calculation is obtained from using approximate values, often rounded to 1 significant figure.

Which of the following is the most accurate estimate calculation for 856 × 465?

Which of the following are good, quick estimate calculations for 578 ÷ 1.785?

Which of the following are good, quick estimate calculations for $${4.56\times8.95} \over {7.65}$$?

Which of the following are correct estimates for $${18.96\times2.15} \over {0.546}$$?

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.

___________ figures are the digits in a number that contribute to the accuracy of the number. 
The first __________ figure is the first non-zero digit.

Sam correctly rounds an integer to the nearest 10. Sam's answer is 80. What could Sam's unrounded integer be?

Laura correctly rounds a number to 1 significant figure. Her answer is 8. What could Laura's unrounded number be?

Estimating numerical calculations

Lesson outcome