Final answer:
The average speed of the journey is calculated by summing the distances traveled at each speed and dividing by the total time. With 4 hours at 27.5 km/h and 7 hours at 48.5 km/h, the average speed is approximately 40.9 km/h. The closest answer choice is (d) 40 km/h.
Step-by-step explanation:
Calculating Average Speed
To find the average speed of a journey that has different speeds for different parts, we must first determine the total distance traveled and then divide it by the total time. The journey consists of 4 hours at 27.5 km/h and then 7 hours at 48.5 km/h. We calculate the distances for each segment as follows:
- Distance1 = Speed1 × Time1 = 27.5 km/h × 4 h = 110 km
- Distance2 = Speed2 × Time2 = 48.5 km/h × 7 h = 339.5 km
- Total Distance = Distance1 + Distance2 = 110 km + 339.5 km = 449.5 km
- Total Time = Time1 + Time2 = 4 h + 7 h = 11 h
We then use the formula for average speed, which is:
Vavg = Total Distance / Total Time
Plugging in the values:
Vavg = 449.5 km / 11 h = 40.8636 km/h
The correct answer rounded to the nearest tenth is 40.9 km/h. However, since none of the answer choices exactly match this value, we choose the closest answer, which is (d) 40 km/h.