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

To change a number into another number that is approximately the same value but is easier to work with. E.g. round 561 to the nearest 10 is 560.

Rounding integers to one significant figure

Maths

Checking understanding of rounding

Securing understanding of rounding

Rounding to three decimal places

Rounding to any number of decimal places

Rounding integers to significant figures

Rounding decimals to significant figures

Degrees of accuracy

Estimating numerical calculations

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

The first significant figure is the first non-{{ }} digit in a number.

Select all the numbers which have 4 as the first significant figure.

In the number 654 023, in which column is the first significant figure?

Match each number to its value when it is rounded to one significant figure.

What value could the missing digit be in 3$$\square$$89 = 4000 (to 1 s.f.)?

A degree of {{ }} shows how precise a number or measurement is. Examples are: to the nearest cm, to the nearest 10, to 1 s.f. and 2 d.p. 

Calculate the cost of carpeting this area.

3 friends go out for lunch and spend £31.  They pay the same amount each.  What is the smallest amount they each pay to cover the cost of the bill?

Rounding integers to one significant figure

Lesson outcome