You are driving at a speed of 25 m/s when an ambulance, approaches from behind at 45 m/s and with a siren frequency of 1,400 Hz. El Niño has
lowered the temperature to a bitter -5°C. You hear a different frequency
from the siren before it passes you compared to after it passes you. What
is the difference in the frequencies you hear?

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.

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