Final answer:
To find the average speed of the marathon runner, convert the time to hours and then use the formula distance divided by time. The runner's average speed is approximately 14.75 km/h, which is answer (a).
Step-by-step explanation:
To calculate the average speed of the runner in the marathon, we can use the formula for speed which is distance divided by time. The distance of the marathon is given as 42.2 km. First, we need to convert the time from hours, minutes, and seconds to hours only. There are 60 minutes in an hour and 3600 seconds in an hour.
Time in hours = 2 hours + (51 minutes / 60) + (55 seconds / 3600) = 2 + 0.85 + 0.01528 ≈ 2.86528 hours
Next, we calculate the average speed using the formula:
Average speed = Total distance / Total time
Average speed = 42.2 km / 2.86528 hours ≈ 14.74 km/h
Therefore, the average speed of the runner is approximately 14.74 km/h which rounds to 14.75 km/h, making the correct answer (a) 14.75 km/h.