QR question

[duvaldentist]

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This question asks if the Diameter is doubled what effect will it have on a spheres volume?

my rational is that D=2R so if D is doubled then you get the following 2D=4R but according to the answer provided if D is doubled then R is doubled but wouldn't doubling D quadruple R?

If you could shed light on this i would greatly appreciate it... Thank you all in advance.

 

[FeralisExtremum]

Volume of a sphere is (4/3) * r^3

Doubling r means that it increases by a factor of 2^3

2^3 = 8

 

[jyjuang]

Think of it this way, say the original radius is 1 and diameter 2. If you double the diameter, which makes it 4. The new radius would be 2, which is also 2 times the original radius.

 

[KyoPhan]