Final answer:
The average speed of the skateboarder is found by dividing the total distance traveled (5 km) by the total time taken (1.5 hours), resulting in approximately 3.33 km/h, which does not match any of the provided options.
Step-by-step explanation:
To calculate the average speed of the skateboarder, you need to divide the total distance traveled by the total time taken. The skateboarder travels 2 km down the sidewalk, 1 km walking up the hill, and 2 km back home, which sums up to a total distance of 5 km. The total time taken is 1.5 hours. To find the average speed:
Average speed = Total distance traveled ÷ Total time of travel
Average speed = 5 km ÷ 1.5 hours = 3.³ km/h
When converted to km/h, the average speed of the skateboarder is approximately 3.33 km/h, which is not one of the options provided. It seems there might be a mistake in the options given or in the interpretation of the question as the correct average speed does not match any of the choices (a) 10 km/h, (b) 15 km/h, (c) 20 km/h, or (d) 25 km/h.