A car travels three-fourth of the distance at the
speed of 25 kmph and the remaining distance at
the speed of 10 kmph. What is the average speed
of the car for entire journey ?
(A) 12.5 kmph
(B) 21.25 kmph
(C) 17.75 kmph
(D) None of these

• Let the total distance be x km.
  Then car travels (3/4)x km with a speed of 25 km/h,
  so time taken during this journey,t1= ((x(3/4))/25) hr = (3x/100) hr.
  remaining distance = ( x - (3x/4)) = (x/4) km ,
  car travels this remaining distance with a speed of 10 km/h,
  time taken during this journey, t2= ((x/4)/10) hr = (x/40) hr.
  total time, T = t1 + t2 = (3x/100) + (x/40) = (11x/200) hr
  avg speed of total journey = ( total distance / total time taken )
  = (x/(11x/200)) = (200/11) = 18.18 km/h
• 10 years agoHelpfull: Yes(1) No(1)
• avg. speed=1/[(3/4)*(1/25)+(1/4)*(1/10)]=200/11 kmph= 18.18 kmph
• 11 years agoHelpfull: Yes(0) No(2)