A learner works out the volume of a cube whose edges are 4 centimetres long and writes: 4 times 4 is 16, so the volume is 16 cubic centimetres. Which statement names the mistake in this volume calculation and gives the correct volume?
Only two edges were used; a cube needs all three, so the volume is 64 cubic centimetres.✓الإجابة الصحيحة
The working is fine, because every face of this cube measures 4 centimetres by 4 centimetres and so the whole solid does too.
The three edges should have been added instead, so the volume is 12 cubic centimetres.
The result should be multiplied by the six faces, giving 96 cubic centimetres.
الشرح
Multiplying two edges measures a single square face, and a solid needs a third edge to give it depth, so 4 has to be multiplied by itself three times. The number 16 counts the little squares on one face and leaves every layer behind that face unaccounted for.