Arjun travelled from A to B by a bus at the speed of 30 kmph and from B to C by a car at the
speed of 70 kmph. What is his average speed for the whole journey from A to C if the
distance between A and B is same as that between B and C?

• 42 kmph
  
  Given speeds 30 kmph and 70 kmph to cross the same distance, then
  Average speed=2ab/(a+b)=2*30*70/(30+70)= 42 kmph.
  
  OR
  Let the distance from A to B and B to C be x km, then
  Average speed=Total distance/ Total time=(x+x)/[(x/30) + (x/70)]=2x/(x/21) = 42 kmph.
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