A car travels up a hill at a constant speed of 45 km/h and returns down the hill at a constant speed of 70 km/h. Calculate the average speed for the round trip.

To calculate the average speed for the round trip, we need to find the total distance traveled and the total time taken.

Let's start by finding the distance traveled while going up the hill. The speed is given as 45 km/h, which means that the car covers a distance of 45 kilometers in one hour.

Next, we need to find the distance traveled while going down the hill. The speed is given as 70 km/h, so the car covers a distance of 70 kilometers in one hour.

Since the car travels the same distance up and down the hill, the total distance for the round trip is twice the distance traveled in one direction. Therefore, the total distance is 2 multiplied by the distance traveled for one direction.

To calculate the total time taken for the round trip, we need to account for the time taken while going up the hill and the time taken while going down the hill. Again, since the distance traveled is the same, the time taken for the round trip is twice the time taken for one direction.

Now, let's calculate:

Distance traveled for one direction: 45 km
Total distance for the round trip: 2 * 45 km = 90 km

Time taken for one direction: 1 hour
Total time taken for the round trip: 2 * 1 hour = 2 hours

Finally, to calculate the average speed, we divide the total distance by the total time:

Average speed = Total distance / Total time
Average speed = 90 km / 2 hours
Average speed = 45 km/h

Therefore, the average speed for the round trip is 45 km/h.