Boats and Streams- Aptitude Questions and Answers

If The speed of boat or boatman in calm water is u kmph and The speed of water or stream is v kmph, then:In water, the speed along with stream= (u + v) kmph

Speed of current = 5 - 3.5 = 1.5 km/hr.

So the speed of man along the current = 5 + 1.5 = 6.5 km/hr

If The speed of boat or boatman in calm water is u kmph and The speed of water or stream is v kmph, then:
Speed downstream= (u + v) kmph , In water, the speed along with stream
Speed upstream = (u - v) kmph ,In water, the speed against the stream

15= u + 1.5
⇒ u = 13.5

Speed upstream, u - v = (13.5 - 1.5) km/hr = 12 km/hr

Speed upstream Speed(S) = Distance(d)/Time(t) = 14/56 km/min = 14*60/56 km/hr= 15 km/hr

If The speed of boat or boatman in still water is U kmph and The speed of water or stream is V kmph, then:
Speed upstream = (U - V) kmph ,In water, the speed against the stream
15 = U - 2
So speed of boat in still water , U = 17 km/hr

Upstream Speed(S) = Distance(d)/Time(t) = 32/4 km/hr= 8 km/hr

If The speed of boat or boatman in still water is U kmph and The speed of water or stream is V kmph, then:
Speed upstream = (U - V) kmph
8 = U - 2
Speed of man in still water,U = 8 + 2 = 10 km/hr

Speed of man in downstream = (U + V) kmph = (10 + 2) = 12 km/hr
Now, man cover the distance in 6 hours = 12 * 6 = 72 km

If the speed downstream is x kmph and the speed upstream is y kmph, then:
Rate of stream = 1/2 (x - y) kmph.

= 1/2(21 - 15) km/h
= 3 km/h

If the speed downstream is x kmph and the speed upstream is y kmph, then:
Speed in still water = 1/2 (x + y) kmph.

x = 60/4 =15 km/h
y = 36/4 = 9 km/h
speed of the man = (15 + 9) / 2 = 12 km/h

Speed Downstream = (15 + 3) km/hr = 18 km/hr.

Distance travelled =(18 * 12 / 60 )hrs = 3.6 km

If The speed of boat or boatman in still water is U kmph and The speed of water or stream is V kmph, then:
Speed upstream = (U - V) = 8 km/hr
Speed of man in downstream = (U + V) kmph = 12 km/hr

After solving above equations 2*U = 20 km/hr
speed of boat in still water is,U = 10 km/hr

Required time = 24 / 10 = 2.4 hr

boat speed = 10 km/hr and stream speed = 5 km/hr
Thus net speed of boat in downstream = 10 + 5 = 15 km/hr

Time taken to travelled 5 km distance

time = distance / speed = 5/ 15 = 1/3 hr = 60/3 minutes = 20 minutes

Let A= Downstream=11km/hr ,
B=Upstream=5km/hr
Speed in still water = 1/2(A + B) km/hr
= 1/2(11+5)km/hr
= 1/2(16)km/hr
= 8km/hr

Let man’s rate upstream be x kmph
then, his rate downstream =3x kmph
Speed in still water, 18 =1/2[3x+x]=2x kmph
x = 9 kmph

Rate upstream, x=9 km/hr,
rate downstream, 3x=27 km/hr
Hence,rate of stream=1/2(27-9)km/hr
=9 km/hr

Let the place be x kms from starting point.
Upstream speed = 7.5–1.5=6 kmph
Downstream speed = 7.5+1.5=9 kmph
Time to row up and down = 50/60 hour

Total time=> x/6 + x/9=50/60 hr
5x/18=5/6
5x=15
x=3 km

The place is at distance of 3 km

three - quarters of a kilometer = 750 meters
and 11(1/4) minutes= 675 seconds

rate upstream = 750/625 m/sec =10/9 m/sec
rate downstream =750/450 m/sec = 5/3 m/sec
rate in still water =1/2[10/9 + 5/3]
= 25/18 m/sec
= 25/18*18/5 km/hr
= 5 kmph

Speed down stream = 13+4 = 17 kmph
time taken to travel 68km downstream = 68/17 hrs
= 4 hrs

Let the speed of the stream be x mph
then, speed downstream = [10+x]mph
speed upstream =[10-x] mph
90 min= 90/60 hrs

As given, 36/[10-x] - 36/[10+x] = 90/60 hrs
36/[10-x] - 36/[10+x] = 3/2 hrs
36*(10+x)- 36*(10-x) = 3(10+x)(10-x)/2
24*(10+x)- 24*(10-x) = (10²-x2)
48x=100-x²
x²+48-100=0
x²+50x−2x−100=0
x(x+50)−2(x+50)=0
(x−2)(x+50)=0
x=−50,2

time cannot be negative.
So, the speed of the stream is 2 mph

Let the speed in still water be x mph and the speed of the current be y mph.
then, speed upstream = (x-y)
speed downstream =(x+y)
12/(x-y) - 12/(x+y) = 6
6(x² - y²) m= 24y
=> x² - y² =4y -------(1)
and 12/(2x-y) - 12/(2x+y) =1
4x² - y² = 24y
=> x²= ( 24y + y²)/4 -------(2)
from 1 and 2 we have
4y+ y² =( 24y+y²)/4
y=8/3 mph ie 2(2/3) mph