Final answer:
To find Norma's average speed, we need to calculate the total distance and total time taken. For the first part of the trip, Norma drives for 150 minutes at 40 km/h. For the second part of the trip, Norma drives for 3.15 hours at 60 km/h. The average speed is 57.23 km/h.
Step-by-step explanation:
To find the average speed, we need to calculate the total distance and total time taken.
For the first part of the trip, Norma drives for 150 minutes at 40 km/h. This means she covers a distance of 40 km/h * (150 min / 60 min/h) = 100 km.
For the second part of the trip, Norma drives for 3.15 hours at 60 km/h. This means she covers a distance of 60 km/h * 3.15 h = 189 km.
The total distance covered is 100 km + 189 km = 289 km.
The total time taken is 150 min + 75 min + 3.15 h = 5.05 hours.
The average speed is calculated by dividing the total distance by the total time taken: 289 km / 5.05 h = 57.23 km/h.