A car covers 1/3 distance with speed 20 km/hr and 2/3 with 60 km/hr. Average speed is1. A. 40 km/hr2. B. 50 km/hr3. C. 36 km/hr4. D. 80 km/hr
Question
A car covers distance with speed 20 km/hr and with 60 km/hr. Average speed is
- A. 40 km/hr
- B. 50 km/hr
- C. 36 km/hr
- D. 80 km/hr
Solution
The average speed of a journey is given by the total distance travelled divided by the total time taken. In this case, the total distance is split into two parts, 1/3 and 2/3, each covered at different speeds.
Step 1: Calculate the time taken for each part of the journey.
For the first 1/3 of the journey, at 20 km/hr, the time taken is (1/3) / 20 = 1/60 hours.
For the remaining 2/3 of the journey, at 60 km/hr, the time taken is (2/3) / 60 = 1/30 hours.
Step 2: Add these times together to get the total time taken.
Total time = 1/60 + 1/30 = 1/20 hours.
Step 3: The average speed is then the total distance (1) divided by the total time (1/20), which gives an average speed of 20 km/hr.
So, none of the options A, B, C, D is correct. The average speed is 20 km/hr.
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