In a journey of 80 kms a train covers the first 60 kms at 40 km/hr. and the remaining distance at 20 km/hr. The average speed for the whole journey is :

Question

Accepted Answer

To determine the average speed for the entire journey, we need to calculate the total distance traveled and the total time taken for the journey.

1. **Distance and Speed Details:**
   - The train covers the first 60 km at a speed of 40 km/hr.
   - The remaining 20 km is covered at a speed of 20 km/hr.

2. **Time Calculation:**
   - Time taken to cover the first 60 km = Distance/Speed = 60 km / 40 km/hr = 1.5 hours.
   - Time taken to cover the remaining 20 km = Distance/Speed = 20 km / 20 km/hr = 1 hour.

3. **Total Time:**
   - Total time for the journey = 1.5 hours + 1 hour = 2.5 hours.

4. **Average Speed Calculation:**
   - Average speed is calculated as Total Distance / Total Time.
   - Total distance = 80 km.
   - Total time = 2.5 hours.
   - Average speed = 80 km / 2.5 hours = 32 km/hr.

Therefore, the average speed for the whole journey is 32 km/hr, which corresponds to Option 3.

**Explanation for Incorrect Options:**

- **Option 1 (24 km/hr):** This option is incorrect because it underestimates the average speed. The calculation shows that the average speed is higher than 24 km/hr.

- **Option 2 (30 km/hr):** This option is incorrect because it does not accurately reflect the calculated average speed. The correct average speed is slightly higher at 32 km/hr.

- **Option 4 (36 km/hr):** This option is incorrect because it overestimates the average speed. The calculated average speed is lower at 32 km/hr.

In conclusion, the correct average speed for the journey is 32 km/hr, making Option 3 the correct choice.