Step 9 Objective

Recognise that measurements given to the nearest whole unit may be inaccurate by up to one half of the unit in either direction.

Examples of what pupils should know and be able to do

Probing questions

If the mass of an object is 60 kg to the nearest whole number, why could its mass be more than that of another object that has a mass of 60 kg to the nearest whole number?

Can anything ever be measured exactly?

What if pupils find this a barrier?

Make links to rounding to the nearest whole number.

If necessary use a number line to explore the range of measures that would be expressed to a given whole unit. Consider problems in context, e.g. if the distance between two towns is 12 miles, what is the minimum distance? What is the maximum distance?