A learner converts 0.5 square metres into square centimetres and writes: one metre is 100 centimetres, so 0.5 times 100 gives 50 square centimetres. Which statement names the mistake in this unit conversion and gives the correct value?
The working is right, because the same hundred links every metric unit with the one below it.
Only the whole-number part of the measurement converts, so the answer should be 100 square centimetres.
Surfaces convert by the length factor multiplied by itself, so 0.5 is multiplied by 10 000, giving 5000 square centimetres.✓Correct answer
Halving one thousand gives the answer, so it should be 500 square centimetres.
Explanation
Half a square metre is half of a square measuring a hundred centimetres each way, and that square contains ten thousand of the smaller squares. Multiplying by a hundred converts one direction only, leaving a patch only about 7 centimetres across each way where half a tabletop belongs.