Q25 of 134 Page 4

A train, travelling at a uniform speed for 360 km, would have taken 48 mins less to travel the same distance, if its peed were 5 km/hr more. Find the original speed of the train.

To find: The original speed of the train.

Formula Used:


The quadratic formula for finding the roots of quadratic equation
ax2 + bx + c = 0, a ≠ 0 is given by,



Explanation:


Let the original speed of the train be x km/hr


Then, the increased speed of the train = (x + 5) km/hr


According to question,


[⸪ ]



⇒


⇒ [5(360x + 1800) – (360x)] = 4x (x + 5)


⇒ 4x2 + 20x – 9000 = 0


⇒ x2 + 5x – 2250 = 0


By using the quadratic formula,






(⸪ Speed cannot be negative)


⸫ The original speed of the train is 45 km/hr.


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