Susan drove for 2 hours at 85 km/hr and then for 3 hours more at 95 km/hr. What was her average speed for the entire trip?
[(2 * 85) + (3 * 95)] / 5 = _____ km/hr
91
To find Susan's average speed for the entire trip, we need to calculate the total distance traveled and divide it by the total time taken.
To calculate the distance traveled during the first part of the trip, we multiply the time (2 hours) by the speed (85 km/hr):
Distance1 = Speed1 * Time1
Distance1 = 85 km/hr * 2 hr
Distance1 = 170 km
Similarly, to calculate the distance traveled during the second part of the trip, we multiply the time (3 hours) by the speed (95 km/hr):
Distance2 = Speed2 * Time2
Distance2 = 95 km/hr * 3 hr
Distance2 = 285 km
Now, we can calculate the total distance traveled:
Total Distance = Distance1 + Distance2
Total Distance = 170 km + 285 km
Total Distance = 455 km
Next, we calculate the total time taken for the entire trip:
Total Time = Time1 + Time2
Total Time = 2 hr + 3 hr
Total Time = 5 hr
Finally, we can calculate the average speed:
Average Speed = Total Distance / Total Time
Average Speed = 455 km / 5 hr
Average Speed = 91 km/hr
Therefore, Susan's average speed for the entire trip was 91 km/hr.