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An engine approaches a hill with a constant speed. When it is at a distance of $0.9\, km$, it blows a whistle whose echo is heard by the driver after $5\, seconds$. If the speed of sound in air is $330\, m/s$, then the speed of the engine is .... $m/s$
  • A$32$
  • B$27.5$
  • C$60$
  • D$30$
JEE MAIN 2013, Diffcult
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