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## 'Funnel' printed from http://nrich.maths.org/

As an example of how you might begin, take one litre as the
volume.

How many cubic centimetres is that ?

If the radius was 1 cm, 2 cm, 3 cm, etc. what would the height
be each time ?

And how long would the 'slope length' be in each case ?

How do you calculate the curved surface area using those things
?

When was the curved surface area least ?

Can you refine your answer with more precise values tried for
the radius length ?

Could a spreadsheet help with the repeated calculation ?