If a truck travelled 300 km at 90 km/h and then returned at 65 km/h, what was the average speed for the journey, correct to one decimal place?

Step 1: Calculate the time taken for each leg of the journey.

For the first leg of the journey, the truck traveled 300 km at 90 km/h. So, the time taken is distance/speed = 300 km / 90 km/h = 3.33 hours.

For the return journey, the truck traveled the same distance at a slower speed of 65 km/h. So, the time taken is distance/speed = 300 km / 65 km/h = 4.62 hours.

Step 2: Calculate the total time taken for the journey.

The total time taken for the journey is the sum of the time taken for each leg. So, total time = 3.33 hours + 4.62 hours = 7.95 hours.

Step 3: Calculate the total distance traveled.

The truck traveled 300 km each way, so the total distance traveled is 2 * 300 km = 600 km.

Step 4: Calculate the average speed.

The average speed is the total distance traveled divided by the total time taken. So, average speed = total distance / total time = 600 km / 7.95 hours = 75.5 km/h.

So, the average speed for the journey, correct to one decimal place, is 75.5 km/h.