a boat covers 72km upstream in 18h in return/jouney it cocers half of the distance at normal downstream but in remaining half distance its downstream speed reduces by 25%if speed of the boat in still water is thrice speed of current then find total time taken by boat covr return journey
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Answer:
15 km/hr
Step-by-step explanation:
Solution 1
Let the speed of the water in still water =
x
Given that speed of the stream = 3 kmph
Speed downstream
=
(
x
+
3
)
kmph
Speed upstream
=
(
x
−
3
)
kmph
He travels a certain distance downstream in 4 hour and come back in 6 hour.
ie, distance travelled downstream in 4 hour = distance travelled upstream in 6 hour
since distance = speed × time, we have
(
x
+
3
)
4
=
(
x
−
3
)
6
⇒
(
x
+
3
)
2
=
(
x
−
3
)
3
⇒
2
x
+
6
=
3
x
−
9
⇒
x
=
6
+
9
=
15
kmph
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