Well there is 1000 metres in a kilometre, and a 100 centimetres in a metre therefore 1000x100 = 100000.
If you know the meaning of the prefixes it becomes so easy kilo=1000, centi=100th, milli=1000th, etc.
1 kilometer=100,000 centimeters
1 kilometer=100,000 centimeters
1 kilometer=100,000 centimeters
1 kilometer=100,000 centimeters
1 kilometer=100,000 centimeters
1 kilometer=100000 centimeters
1 kilometer=100,000 centimeters
1 kilometer=100,000 centimeters
67.3 kilometers = 6,730,000 centimeters
1 kilometer=100,000 centimeters
1 kilometer=100,000 centimeters
1 kilometer=100,000 centimeters