Give the step-by-step reasoning process and then the final answer. Emma traveled by car 280 miles in 2 hours 20 minutes. What was the average speed of the car in miles per hour?
We first convert the time of 4 hours 20 minutes in minutes 2 hours 20 minutes = 2 × 60 + 20 = 140 minutes. Average speed S is given by distance / time. Hence S = 280 miles / 140 minutes = 2 mile / minute. There are 60 minutes in an hour so the speed is 2 * 60 = 120 miles / hour.
The final answer: 120.