

A sphere's volume and area are 1/2 that of its box - bumbledraven
http://www.vendian.org/envelope/dir0/ballbox.html

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gus_massa
I disagree. It's good that children know that the volume and area of a sphere
is something with pi (and can search the exact constant in Wikipedia).

I like the idea that the volume of a sphere is half of the volume of the box.
I never thought about it. But this is more useful as a rule of thumb and a
trick to remind the actual formula:

* It's a volume, so it's something like r^3

* It's round, so it has a pi

* Half of the box is 1/2 (2r)^3 = 4r^3

* Now: X * pi * r^3 ~= 4 r^3

* And pi ~= 3 so, X * 3 = 4, then X=4/3 and V=4/3 pi r^3

