This week’s #MondayMaths: volume estimation

Blog: Vicki Robinson, Communications Officer

This week’s #MondayMaths: volume estimation

Posted: 8/08/16

While many of us wouldn’t admit to having a big head – ever wondered how big yours actually is?!

This week’s #MondayMaths problem is all about estimation. We’re asking puzzle-solvers to estimate the volume of everyday objects (including a human head!) and place them in size order.

Students following our mastery curriculum aren’t formally taught the formulae for the volumes of spheres until Key Stage 4 but estimation is a concept worked on in Autumn 1 of Year 7 using rounding, It’s then applied in more depth in Summer 1 of Year 8 where students look at significant figures and estimation in measurement.

In primary, pupils begin to estimate in Year 2 and round in Year 4. In Year 5, pupils estimate volume (using 1cmblocks to build cuboids, for example). In Year 6, pupils calculate, estimate and compare volume of cubes and cuboids using standard units.

A quick tip

Start with the more commonly shaped objects first – the shoebox, Pringles tube and football are all simple 3D shapes that (with a formula sheet if needed) should be simple to calculate.

Making decent estimates of dimensions is important. It’s a good idea to talk about how to estimate, perhaps by comparing the objects to shapes which can be measured.

When estimating the slightly trickier volumes of the human head and bicycle tyre, there’s an extra layer involved: approximating the shape of the object.

With the human head, students are likely to approximate the volume based on a sphere or cylinder. Hopefully, those tackling the puzzle will be able to see that the tyre is simply an encircled cylinder and use the circumference formula to estimate the length of the cylinder.

Justify your method

Remember there are no right answers, but it’s important to justify any estimations and calculations as well as talk about whether the values found are surprising.

As we do each week, the full solution, along with our estimations, will be posted on Thursday morning on Twitter.

We love seeing how you and your pupils tackled the problems so please do share your work. Good luck and enjoy!

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