01
Radius and diameter swapped under pressure
Not carelessness — the two lengths were never attached to a drawing they own.
Topic hub
Mensuration
Mensuration is measurement of length, area and volume in increasingly three-dimensional shapes. Children struggle when the formula is memorised without a picture of what is being measured — especially radius vs diameter, and nets vs solids.
Why this concept matters
Board papers love a cylinder that is also a story about a tank. The story is easy if the picture is there.
Misconceptions, in the order we see them
02
Volume is ‘the big formula’
They cannot say they are stacking area.
03
A net is arts and crafts
The connection between the solid and the flattened faces is not used to find area.
Which classes cover this
Related: Fractions · Decimals · Percentages · Ratio and proportion · Integers
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