A boat whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is:
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Answer:
Speed of the stream is 5km/hr
Step-by-step explanation:
Let the speed of the stream be x km/hr
Then Speed of boat downstream =(15+x) km/hr
Speed of boat upstream =(15−x) km/hr
Therefore,
15+x
30
+
15−x
30
=4
2
1
=
2
9
⇒
(15+x)(15−x)
30(15−x)+30(15+x)
=
2
9
⇒
225−x
2
900
=
2
9
⇒200=225−x
2
⇒x
2
=25
⇒x=5 km/hr
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