Find the ratio between the speeds of the boat and stream if the boat can travel 30 km upstream in 3 hours and the same distance downstream in 2 hours.
A)
5:1
B)
3:2
C)
4:1
D) 02:03:
Correct Option - A
Explanation
u = 10 kmph
d = 15 kmph
s = (d-u)/2 = 2.5 kmph
b = (d+u)/2 = 12.5 kmph
b:s = 5:1
Moving along a stream, a boat travels 16 km and moving against the stream, it travels 12 km. The time taken for the entire journey is 5 hours. The upstream speed and
A)
8 kmph
B)
4 kmph
C)
2 kmph
D)
6 kmph
Correct Option - C
Explanation
16/d) + (12/u) = 5
d=2u
s = (d-u)/2
Solving, s = 2 kmph
A boatman starts from point A at 11:00 am and travels downstream to point B, stays there for an hour and returns to point A at 4:00 pm. If the speed of the boat and stream are
A)
45 km
B)
22.5 km
C)
36 km
D)
27 km
Correct Option - D
Explanation
Upstream and downstream travel took him 4 hours (leaving his 1 hour stay at B).
u = 9 km/hr
d = 15 km/hr
(x/9) + (x/15) = 4
Distance = 22.5 km
The effective speed of travel of a boat downstream is 18 kmph whereas it is 10 kmph upstream. What is the speed of the current?
A)
14 kmph
B)
8 kmph
C)
4 kmph
D)
5 kmph
Correct Option - C
Explanation
Speed of the current
= (d-u)/2
= (18-10)/2
= 4 kmph
A swimmer swims 5 km upstream and 3 km downstream in 1 hour. If the speed of the stream is 3 kmph, find the swimmer's speed.
A)
6 kmph
B)
5 kmph
C)
4.5 kmph
D)
7.5 kmph
Correct Option - A
Explanation
Let swimmer's speed=x kmph
Time taken to swim downstream
= 5/(x-3)
Time taken to swim upstream
= 3/(x+3)
[5/(x-3)]+[3/(x+3)] = 2
5x+15+3x-9 = 2(x²-9)
2x²-8x-24=0
x²-4x-12=0
(x-6)(x+2)=0
x can't be -2
Hence, x=6 kmph
The speed of a boat in still water is 20 kmph and the speed of the stream is 5 kmph. The distance travelled upstream in 20 minutes is
A)
15 km
B)
10 km
C)
3 km
D)
5 km
Correct Option - D
Explanation
u = 15 kmph
Distance = 15*20/60 = 5 km
A boat travels 10 km upstream and 5 km downstream in 3 hrs. If the speed of the boat in still water is 7 kmph, find the speed of the stream.
A)
2 kmph
B)
3 kmph
C)
4 kmph
D)
5 kmph
Correct Option - B
Explanation
Let the speed of the stream be x kmph.
Upstream speed = (7-x) kmph
Downstream speed = (7+x) kmph
Time taken to travel upstream = (10/(7-x)) hrs
Time taken to travel upstream = (5/(7+x)) hrs
(10/(7-x)) + (5/(7+x)) = 3
3x2+5x-42=0
Solving this equation, x=3