Final answer:
To find how long it will take a runner to complete a marathon at a constant speed of 12.0km/h, convert 26.2 miles to kilometers and then divide by the speed. The answer is approximately 3 hours, 30 minutes, and 49 seconds.
Step-by-step explanation:
The question asks: if a runner maintains a constant speed of 12.0km/h, how long will it take him to complete a marathon race of 26.2 miles? To solve this, we first need to convert the marathon distance from miles to kilometers, since the runner's speed is given in kilometers per hour. There are approximately 1.60934 kilometers in a mile.
Therefore, the marathon distance in kilometers is 26.2 miles × 1.60934 km/mile = 42.164868 km. Now, we can use the formula time = distance/speed to find the runner's time.
The runner's speed is 12.0 km/h, and the marathon distance is 42.164868 km.
Time = 42.164868 km / 12.0 km/h = 3.513739 hours.
To convert hours into minutes, we multiply by 60, since there are 60 minutes in an hour:
3.513739 hours × 60 minutes/hour = 210.82434 minutes,
or 3 hours, 30 minutes, and approximately 49 seconds.