Rounding means to change a number into another number that is approximately the same value but is easier to work with.

A degree of accuracy shows how precise a number or measurement is.  E.g to the nearest cm, nearest 10, 1 s.f., etc.

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.

Truncation is when we simplifying a number by 'cutting off' one or more of the digits and replacing them with zeros if necessary to preserve place value.

Checking and securing understanding of rounding and truncating

Maths

In the prior unit, pupils 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 this unit, pupils will investigate the bounds and perform calculations to determine a best/worst case scenario.

This unit explores the impact of upper and lower bounds on additive and multiplicative calculations.

Rounding, estimation and bounds

Truncation is when we simplifying a number by 'cutting off' one or more of the digits and replacing them with {{ }} if necessary to preserve place value. 

The mass of an elephant is 5000 kg when given to the nearest 1000 kg.  Which of the following would not be the mass of an elephant?

Round 345 678 to the nearest ten thousand.

Round each of the following to 2 significant figures.

Which of the following do not give the same answer when rounded to 2 significant figures or truncated to 2 significant figures?

Aisha writes 2684 as approximately 3000.  Aisha has written it to the nearest {{ }}.

Which digit is in the ten thousands column in 742 683?

Which digit is in the hundredths column in 129.083?

In the number 3 547 028, which column is the digit 5 in?  

In the number 123.4567, which column is the 6 in?

This lesson will be removed by end of Summer Term 2025.

Checking and securing understanding of rounding and truncating

Lesson outcome

This lesson will be removed by end of Summer Term 2025.