Step 1. 1000 m = 1 km and 100 cm= 1 m or 10000 cm = 1 km
Step 2. 72 km/h * 1000 m/km * 100 cm/m = 7,200,000 cm/h (note the units cancel in km and m when multiplying the units together.
Step 3. Answer is 7.2 million cm/h
I hope the above steps were helpful.
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