A man goes to Jaipur from Surat at a speed of 20km/hr and returns to Surat at speed of 30km/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. 24.
Let distance between Surat and Jaipur = D km
Time to go = D ÷ 20
Time to return = D ÷ 30
Total distance = D + D = 2D
Total time = D/20 + D/30 = (3D + 2D)/60 = 5D/60 = D/12
Average speed = Total distance ÷ Total time
= 2D ÷ (D/12) = 2D × 12/D = 24 km/hr