6. A can row a certain distance down a stream in 6 hrs. and return the same distance in 9 hours. If the stream flows at the rate of 2.25 km per hour,
find how far he can row in an hour in still water.
Answers
Answered by
0
Answer:
Letthedistancetravelled=dkm
Giventhatthespeedoftheboatinstillwater=6km/hrand
thespeedofthewatercurrent=2km/hr.
∴Therelativespeeddownstream=(6+2)km/hr=8km/hr.
Sothetimetakendownstream=
relativespeed
distance
=
8
d
hr.
∴
Againtherelativespeedupstream=(6−2)km/hr=4km/hr.
thetimetakenupstream=
relativespeed
distance
=
4
d
hr.
∴Thetotaltimeforgoingdownandcomingup
=(
8
d
+
4
d
)=
8
3d
hr
Alsothetotaldistanceforgoingdownandcomingup=d+d=2d.
∴Averagespeed=
totaltimetaken
totaldistance
=
8
3d
2d
=
3d
2d×8
km/hr=
3
16
km/hr.
Ans−OptionB.
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