We don't use the centimetre when we talk about how far it is to drive from Cambridge to London. Instead the mile or perhaps kilometre is more sensible. The kilometre is exactly equal to 1,000 metres, and we normally write: 1 km = 1,000 m The "k" in this case means "kilo" and is a prefix that makes the unit after it 1,000 times bigger. It can be used with any other unit: e.g. 1 kJ = 1,000 J (joules)
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