Multiple choice general knowledge math & puzzles

A car covers a certain distance at a speed of 90 km/hr while going and returns to the starting point at a speed of 60 km/hr. Find the average speed of the car for the whole journey?

  1. 70

  2. 68

  3. 72

  4. 74

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Average speed for round trip = 2xy/(x+y) where x=90 and y=60. Average = (2×90×60)/(90+60) = 10800/150 = 72 km/hr. The harmonic mean formula applies because distances are equal, not times.