A boat takes 150 min less to travel 40 km downstream than to travel the same distance upstream. The speed of the stream is 4 km/hr. What is the downstream speed?
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Answer:
16 km/hr
Step-by-step explanation:
Let say boat speed = x km/hr
Stream speed = 4 km/jr
upstream speed = x-4 km/hr
downstream speed = x+4 km/hr
Distance one side = 40 km
Upstream time = 40 / (x-4) hr
Downstram time = 40/(x+4) hr
150 min = 5/2 hr
40/(x-4) - 40/(x+4) = 5/2
80 (x+4 - x +4) = 5(x+4)(x-4)
16*8 = x^2 - 16
x^2 = 144
x = 12 km/hr
Downstream speed = 12+4 = 16km/Hr
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