Arace-boat covers a distance of 60 km downstream in one and a half hour. It
covers this distance upstream in 2 hours. The speed of the race-boat in still
water is 35 km/hr. Find the speed of the stream.
Answers
Answer:
speed of the stream is
5
km/hr.
Step-by-step 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.
Another way
Going upstream, the speed of the stream is deducted from speed of the boat i.e
(
35
−
x
)
km/hr
Hence goes
(
35
−
x
)
km in 1 hr.
Therefore for a distance of
60
km Time =
60
35
−
x
hrs.
As per question, Time is 2 hours, so
60
35
−
x
=
2
or
60
=
2
(
35
−
x
)
[ cross multiplication]
or,
60
=
70
−
2
x
or
2
x
=
70
−
60
x
=
10
2
=
5
So, speed of the stream is
5
km/hr.
Answer:
5 km/h
Step-by-step explanation:
let the speed of the stream be "x"
hence when the boat will move upstream, stream will decrease the speed of the boat and when the boat will be coming downstream it will increase the speed of the boat.
Distance = speed * time
60 = (35-x) × 2 [equation for upstream]
x = 5