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.
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,
∴ The original speed of the train is 45 km/hr. (* Speed cannot be negative)
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