Question

race boat covers a distance of 60 kilometre downstream in one and half hour. it covers this distance upstream in 2 hrs. the speed of the race boat in still water is 35 km per hour. find the speed of the stream

Answer 1

Answer:
5
km/hr
Explanation:
As the speed of the boat in still water is known to us we can calculate the speed of the stream either any stream i.e. down stream or up stream.
Say, the speed of the stream is
x
km/hr.
Going downstream the speed of the boat and the speed of the stream will be added together i. e.
(
35
+
x
)
km/hr
Hence the boat goes
(
35
+
x
)
km in 1 hr.
For a distance of 60 km, the Time
=
60
35
+
x
hr
so,
60
35
+
x
=
1
1
2
=
3
2
or,
3
(
35
+
x
)
=
2
⋅
60
[cross multiplication]
or,
105
+
3
x
=
120
or
3
x
=
120
−
105
or,
x
=
15
3
=
5
Speed of the stream is 5 km/hr.