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A train is moving on a straight track with speed 20 ms –1 . It is blowing its whistle at the frequency of 1000 Hz. The percentage change in the frequency heard by a person standing near the track as train passes him is (speed of sound = 320 ms –1 ) close to -

1. 6 %
2. 12 %
3. 18 %
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Correct answer: 12 %

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