A man goes to Ahmedabad from Kolkata at a speed of 78km/hr and returns to Kolkata at speed of 91km/hr, through same route. What is his average speed (in km/hr) of the entire journey?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 84.
Average speed = 2xy/(x + y)
Where:
x = 78 km/hr (Kolkata → Ahmedabad)
y = 91 km/hr (Ahmedabad → Kolkata)
Average speed = (2 × 78 × 91)/(78 + 91)
Average speed = 14,196/169 = 84 km/hr