Calculating the average speed of a car

To calculate the average speed of a car that covers 2/3 of the distance with 60 km/h and 1/3 of the distance with 20 km/h, follow these steps:

Step 1: Calculate the distance covered at each speed

- Let's assume that the total distance covered by the car is 300 km (this is not given in the original question).
- 2/3 of the distance is 200 km, covered at 60 km/h. Using the formula distance = speed x time, we can calculate the time taken as follows:
- time = distance / speed
- time = 200 / 60
- time = 3.33 hours
- 1/3 of the distance is 100 km, covered at 20 km/h. Using the same formula, we can calculate the time taken as follows:
- time = distance / speed
- time = 100 / 20
- time = 5 hours

Step 2: Calculate the total time taken

- To calculate the total time taken, we simply add the time taken at each speed:
- total time = 3.33 + 5
- total time = 8.33 hours

Step 3: Calculate the average speed

- The average speed is given by the formula:
- average speed = total distance / total time
- We already assumed that the total distance covered by the car is 300 km. Plugging in the values, we get:
- average speed = 300 / 8.33
- average speed = 36.02 km/h

Explanation:

The car travelled 2/3 of the distance at a higher speed of 60 km/h and 1/3 of the distance at a slower speed of 20 km/h. Therefore, the time taken to cover the 2/3 distance is less than the time taken to cover the 1/3 distance. To calculate the average speed, we need to consider the total distance covered and the total time taken. Since the car covers a greater distance at a higher speed, the average speed is closer to the higher speed.

In this case, the average speed is 36.02 km/h, which is closer to the higher speed of 60 km/h. This is because the car covers more distance at the higher speed.