correct answer is : c) 6 hours

Answer

Let, the train own speed = x km/hr
According to the question,
In 15 hours, the train reached a place at KaTeX parse error: KaTeX doesn't work in quirks mode. of its own speed.

We know,
Distance = Speed KaTeX parse error: KaTeX doesn't work in quirks mode. Time

KaTeX parse error: KaTeX doesn't work in quirks mode. The distance to the destination is
KaTeX parse error: KaTeX doesn't work in quirks mode. km
KaTeX parse error: KaTeX doesn't work in quirks mode. km
KaTeX parse error: KaTeX doesn't work in quirks mode. km
KaTeX parse error: KaTeX doesn't work in quirks mode. km

KaTeX parse error: KaTeX doesn't work in quirks mode. Time taken the train to reach its own speed is
KaTeX parse error: KaTeX doesn't work in quirks mode.
KaTeX parse error: KaTeX doesn't work in quirks mode. 6 hours.

Ans: Time taken the train to reach its own speed is 6 hours.