Final answer:
To find Justin's average speed overall, we calculate the total distance traveled and total time taken. Justin's average speed is approximately 12.59 mph. correct option is A.
Step-by-step explanation:
To find Justin's average speed, we need to calculate the total distance he traveled and the total time it took him.
First, Justin rides 8 miles at 25 mph, which takes him 8/25 = 0.32 hours. Next, Justin goes 40 mph for 10 minutes, which is equivalent to 40/60 = 0.667 hours. Then, Justin rides 12 miles at 20 mph, which takes him 12/20 = 0.6 hours.
Now, we can find the total distance: 8 + 12 = 20 miles. And we can find the total time: 0.32 + 0.667 + 0.6 = 1.587 hours. To find the average speed, we divide the total distance by the total time: 20/1.587 ≈ 12.59 mph.
Therefore, Justin's average speed overall is approximately 12.59 mph.