**Upstream:**In water, the direction against the stream is called upstream.**Downstream:**In water, the direction along the stream is called downstream.- Let the speed of a boat in still water be u km/hr and the speed of the stream be v km/hr, then:
- Speed downstream = (u + v) km/hr
- Speed upstream = (u - v) km/hr.

- Let the speed downstream be a km/hr and the speed upstream be b km/hr, then:
- Speed in still water =1/2(a+b) km/hr
- Rate of stream = 1/2(a−b) km/hr

- A man can row a boat in still water at x km/hr in a stream flowing at y km/hr. If it takes him t hours to row a place and come back, then the distance between the two places = t(x
^{2}−y^{2}) / 2x km - A man takes n times as long to row upstream as to row downstream the river. If the speed of the man is x km/hr and the speed of the stream is y km/hr, then x = y(n+1) / (n−1)

- A boat takes 28 hours for travelling downstream from point A to point B and coming back to point C midway between A and B. If the velocity of the stream is 6km/hr and the speed of the boat in still water is 9 km/hr, what is the distance between A and B?

A. 115 kms

B. 120 kms

C. 140 kms

D. 165 kms - Speed of a man in still water is 5 km/hr and the river is running at 3km/hr. The total time taken to go to a place and come back is 10 hours. What is the distance travelled?

A. 10 kms

B. 16 kms

C. 24 kms

D. 32 kms - A boat running upstream takes 9 hours 48 minutes to cover a certain distance, while it takes 7 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively?

A. 5:2

B. 7:4

C. 6:1

D. 8:3 - A boat can travel 20 km downstream in 24 min. The ratio of the speed of the boat in still water to the speed of the stream is 4 : 1. How much time will the boat take to cover 15 km upstream?

A. 20 mins

B. 22 mins

C. 25 mins

D. 30 mins - A boat whose speed in 20 km/hr in still water goes 40 km downstream and comes back in a total of 5 hours. The approx. speed of the stream (in km/hr) is:

A. 6 km/hr

B. 9 km/hr

C. 12 km/hr

D. 16 km/hr - A boat covers a certain distance downstream in 2 hour, while it comes back in 2 1/2 hours. If the speed of the stream be 5 kmph, what is the speed of the boat in still water?

A. 40 kmph

B. 30 kmph

C. 35 kmph

D. 45 kmph - A boat running downstream covers a distance of 40 km in 5 hrs and for covering the same distance upstream it takes 10 hrs. What is the speed of the stream?

A. 5 km/hr

B. 2 km/hr

C. 6 km/hr

D. 4 km/hr - A boat goes 4 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 15 km in stationary water?

A. 2 hours

B. 2 hours 15 mins

C. 3 hours

D. 3 hours 30 mins - A man rows to a place 40 km distant and come back in 9 hours. He finds that he can row 5 km with the stream in the same time as 4 km against the stream. The rate of the stream is:

A. 1 km/hr

B. 1.5 km/hr

C. 2 km/hr

D. 2.5 km/hr - A man can row 8 km/hr in still water. When the river is running at 4 km/hr, it takes him 2 1/3hr to row to a place and come back. How far is the place?

A. 4 kms

B. 5 kms

C. 7 kms

D. 10 kms

Downstream speed = 9+6 = 15

Upstream speed = 9-6 = 3

Now total time is 28 hours

If distance between A and B is d, then distance BC = d/2

Now distance/speed = time, so

d/15 + (d/2)/3= 28

Solve, d = 120 kms

Down speed= 5+3= 8

Up speed= 5-3=2

Let distance travelled = X

(X/8)+(X/2)= 10

X = 16 kms

Total distance is 16+16 = 32 kms

Distance covered upstream in 9 hrs 48 min = Distance covered downstream in 7 hrs

(X-Y) 49/5 = (X+Y) 7

X/Y = 1/6

Down speed =20/24*60=50km/hr

4:1 =4x:x

Downstream speed = 4x+x=5x

Upstream speed = 4x-x=3x

5x= 50; x=10

so up speed 3*10=30

Time = 15/30*60= 30 mins

Let the speed of the stream be x km/hr. Then,

Speed downstream = (20 + x) km/hr,

Speed upstream = (20 – x) km/hr.

40/20+x + 40/20-x = 5

X = 9 km/hr appx.

Let the speed of the boat in still water be x kmph. Then,

Speed downstream = (x + 5) kmph,

Speed upstream = (x – 5) kmph.

(x + 5)*2 = (x – 5)*5/2

X = 45 kmph

Downstream speed = 40/5 = 8 km/hr

Upstream speed = 40/10 = 4 km/hr

So speed of stream = 1/2*(8-4)

Rate downstream = 1/10 * 60 = 6kmph

Rate upstream = 4 km/hr.

Speed in still water = ½ * 10 = 5 kmph

Required time = 15/5 = 3 hours

Speed downstream = 5/x

Speed upstream = 4/x

40/(5/x) + 40/(4/x) = 9

X = ½

So, Speed downstream = 10 km/hr, Speed upstream = 8 km/hr

Rate of the stream = 1/2 * 2 = 1 km/hr

Downstream speed = 8+4= 12 => a

Upstream speed = 8-4= 4 => b

Distance = a*b/(a+b) * total time (t)

= 12*4/16 * 7/3

= 7 kms

Quantitative Aptitude Made Simpler

Quantitative Aptitude Made Simpler

Quantitative Aptitude Made Simpler

Quantitative Aptitude Made Simpler

Quantitative Aptitude Made Simpler

Quantitative Aptitude Made Simpler

Quantitative Aptitude Made Simpler

Quantitative Aptitude Made Simpler

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