Sally travels by car from one city to another. She drives for 30.0 min at 80 km/h, 12 min at 105 km/h, and 45 min at 40 km/h. She spends 13.0 min eating lunch and buying gas. what the average speed for the trip?
To find the average speed for the trip, we need to calculate the total distance traveled and the total time taken.
Let's calculate the distance for each leg of the trip:
For the first leg, Sally drives for 30.0 minutes at a speed of 80 km/h. The formula to calculate distance is Distance = Speed × Time. So, the distance for the first leg is:
Distance1 = 80 km/h × (30.0 min / 60 min/h) = 40 km
For the second leg, Sally drives for 12 minutes at a speed of 105 km/h. Using the same formula, the distance for the second leg is:
Distance2 = 105 km/h × (12 min / 60 min/h) = 21 km
Similarly, for the third leg, Sally drives for 45 minutes at a speed of 40 km/h. The distance for this leg is:
Distance3 = 40 km/h × (45 min / 60 min/h) = 30 km
Now, let's calculate the total distance by adding up the distances for each leg:
Total Distance = Distance1 + Distance2 + Distance3 = 40 km + 21 km + 30 km = 91 km
Next, let's calculate the total time taken for the trip:
Sally spends 13.0 minutes eating lunch and buying gas. Adding this time to the driving time, we have:
Total Time = (30.0 min + 12 min + 45 min) + 13.0 min = 100 min
Finally, we can find the average speed by dividing the total distance by the total time:
Average Speed = Total Distance / Total Time = 91 km / (100 min / 60 min/h) = 54.6 km/h
Therefore, the average speed for the trip is 54.6 km/h.
averagespeed=total distance/totaltime
Total time=.5+12/60+45/60+13/60
total distance: figure each (time*speed), and add.