Final answer:
To find the average speed of an Earth's plate in miles per million years, one must first convert the given speed in centimeters per year to kilometers per million years and then to miles per million years, resulting in approximately 12.4 miles per million years.
Step-by-step explanation:
The student's question involves the conversion of units from centimeters per year to miles per million years. This task is common in earth science topics when discussing the movement of tectonic plates. To determine the speed of an Earth's plate in miles per million years given its speed in centimeters per year, we have to perform a series of conversions.
Step-by-Step Explanation
First, we convert the speed from centimeters per year to centimeters per million years by multiplying by 1,000,000, which gives us:
Speed in cm/million years = 2.0 cm/year × 1,000,000 years/million years = 2,000,000 cm/million years
Next, we convert centimeters to kilometers by dividing by 100,000 (since there are 100,000 centimeters in a kilometer), yielding:
Speed in km/million years = 2,000,000 cm/million years / 100,000 cm/km = 20 km/million years
Lastly, we convert kilometers to miles by multiplying by the conversion factor 0.621371 (since 1 kilometer is approximately 0.621371 miles), thus:
Speed in miles/million years = 20 km/million years × 0.621371 miles/km = 12.42742 miles/million years
Therefore, the average speed of an earth's plate is approximately 12.4 miles per million years when rounded to one decimal place.