Final answer:
To determine the distance the Atlantic Ocean will spread in a million years, multiply the annual spread rate of 3 centimeters by a million. After converting centimeters to kilometers, the calculated spread over a million years is approximately 30 kilometers.
Step-by-step explanation:
If the Atlantic Ocean is widening at a rate of 3 cm per year, to calculate how far it will spread in a million years, you simply multiply the rate of spread by the number of years.
First, convert the rate to kilometers by dividing by 100,000 (since 100 cm = 1 m and 1,000 m = 1 km), so 3 cm per year is equal to 0.00003 km per year. Then multiply this by a million years.
0.00003 km/year × 1,000,000 years = 30 km over a million years.
Thus, in a million years, the Atlantic Ocean will have spread approximately 30 kilometers.