Question

A man driving at 72 kmph on a straight road heading towards a hill. He sounds the horn and hears the echo after 4
s. The distance from the hill where the horn was sounded is d. Then d/180 is__ (speed of sound 340 m/s)

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Answer 1

Answer:

What is d / 180???

He is traveling at 72000 m/hr / 3600 sec/hr = 20 m/s

In 4 s he travels 80 m

So the total distance the sound travels is   d + (d - 80) = 2 d - 80

So  (2 d - 80) / 340 = 4         time taken for sound travel

2 d = 1280 m

d = 640 m