EPFO 2012 Solved Paper

Question : 5 of 100

Marks: +1, -0

A train travels at a certain average speed for a distance of 63 km. There after it travels a distance of 72 km with an average speed of 6 km/h more than the original speed. Total time taken to complete the journey is 3 hours. What is the original average speed of the train?

36 km/h
42 km/h
48 km/h
54 km/h

Validate

Solution:

Let the original average speed of the train = x km/h
According to the question,

{63/x+{72}/{x+6}}=3

\{\time={\text"distance"}/{\text"speed"}\}

⇒

9[7/x+8/{x+6}]=3

⇒

3[{7x+42+8x}/{x^{2}+6x}]=1

⇒

45x+126+=x^{2}+6x

⇒

x^{2}-39x-126=0

⇒

x^{2}-42x+3x-126=0

⇒x(x-42)+3(x-42)=0

⇒ x(x-42)(x+3)=0

∴ \ x=42,-3

Hence, the original average speed of the train is 42 km/h.

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