A tourist van travels the distance of 35 km from Dehradun to Mussoorie at an average speed of 36 km/h and returns at 60 km/h. What is the approximate average speed (in km/h) of the tourist van for the entire journey?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3. i.e. 45.
Average speed = Total distance/Total time
Time taken to go from Dehradun to Mussoorie = 35/36
Time taken to go from Mussoorie to Dehradun = 35/60
Average speed = (35 + 35)/(35/36 + 35/60)
⇒ 70/(175 + 105)/180
⇒ 70/280/180
⇒ (70 × 180)/280
⇒ 45 km/hr