In order to determine how many centimeters are in 124.5 km, use the following equivalence:
1 km = 1000 m
1 m = 100 cm
Then, you can multiply for the corresponding conversion factors as follow:
[tex]124.5\operatorname{km}\cdot\frac{1000m}{1\operatorname{km}}\cdot\frac{100\operatorname{cm}}{1m}=12,450,000\operatorname{cm}[/tex]
Hence, there are 12,450,000 centimeters in 124.5 kilometers
