Discuss Forum

1.

The respective ratio between the speed of a car , a train , and a bus is 5 : 9 : 4 . The average speed of the car, bus and train is 72 km / hr together . what is the average speed of the car and the train together?

  • A. 82 km /hr
  • B. 82 km /hr
  • C. 82 km /hr
  • D. 82 km /hr

Answer: Option D

Explanation:

Let the speeds of the car, train and bus be 5x, 9x and 4x km/hr respectively.
Average speed = (5x + 9x + 4x)/3 = 18x /3 = 6x km/hr.
Also, 6x = 72 = > x = 12 km/hr
Therefore, the average speed of the car and train together is = ( 5x + 9x)/2 = 7x = 7 x 12 = 84 km/hr.

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