Question 1

Find the speed of stream if a boat covers 36 km in downstream in 6 hours which is 3 hours less in covering the same distance in upstream?

Accepted Answer

Speed of the boat upstream = 36/9 = 4 kmph Speed of the boat in downstream = 36/6 = 6 kmph Speed of stream = 6-4/2 = 1 kmph

Question 2

A man can row against the current three fourth of a kilometer in 15 min and returns same distance in 10 min, then ratio of his speed to that of current?

Accepted Answer

Let the speed of the man in still water = p kmph Speed of the current = s kmph Now, according to the questions (p + s) x 10 = (p - s) x 15 2p + 2s = 3p - 3s => p : s = 5 : 1 Hence, ratio of his speed to that of current = 5:1.

Question 3

A man swims downstream 72 km and upstream 45 km taking 9 hours each time; what is the speed of the current ?

Accepted Answer

72 --- 9 ? ---- 1 => Down Stream = 8 45 ---- 9 ? ---- 1 => Up Stream = 5 Speed od current S = ? S = (8 - 5)/2 = 1.5 kmph.

Question 4

A person can row 8 1/2 km an hour in still water and he finds that it takes him twice as long to row up as to row down the river. The speed of the stream ?

Accepted Answer

Given speed of the person = 8 1/2 = 17/2 kmph Let the speed of the stream = x kmph speed of upstream = 17/2 - x speed of downstream = 17/2 + x But given that, 2(17/2 - x) = 17/2 + x => 3x = 17/2 => x = 2.83 kmph.

Question 5

Amith can row a boat d km upstream and the same distance downstream in 5 hours 15 minutes. Also, he can row the boat 2d km upstream in 7 hours. How long will it take to row the same distance 2d km downstream for Amith ?

Accepted Answer

Let the speed of boat and stream be x and y kmph respectively. According to question d/x+y + d/x-y = 5h 15m or 21/4 hrs ......(i) and 2d/x-y = 7...... (ii) From eq. (i) and (ii) 2d/x+y = 7/2 Hence, Amith will take to row 2d km distance downstream in 7/2 hrs = 3.5 hrs = 3 hrs 30 min.

Question 6

A motorboat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the motorboat and speed of the water current respectively?

Accepted Answer

8:3

Question 7

Sravan drove from home to a neighboring town at the speed of 50 km/h and on his returning journey, he drove at the speed of 45 km/h and also took an hour longer to reach home. What distance did he cover?

Accepted Answer

Let the distance he covered each way = d kms According to the question, d/45 - d/50 = 1 => d = 450 kms. Hence, the total distance he covered in his way = d + d = 2 d = 2 x 450 = 900 kms.

Question 8

A Woman’s downstream swimming rate is thrice of her upstream swimming rate. If she covers 12 km upstream in 2.5 hours, what distance she will cover in 5 hours downstream?

Accepted Answer

Rate of her upstream = 12/2.5 = 4.8 km/hr Then, ATQ Rate of downstream = 4.8 x 3 = 14.4 km/hr Hence, the distance she covers downstream in 5 hrs = 14.4 x 5 = 72 kms.

Question 9

A boat can move 5 km/hr in still water. If the river is running at 1 km/hr, it takes it 75 min to move to a place and back. How far is the place?

Accepted Answer

Let the place be at a distance of 'd' kms From the given data, d 5 - 1 + d 5 + 1 = 75 60 kms d 4 + d 6 = 5 4 5d/12 = 5/4 => d = 3 kms. Hence, the place is 3 kms far.

Question 10

A motorboat takes half time to cover a certain distance downstream than upstream. What is the ratio between rate of current and rate of boat in still water?

Accepted Answer

Let the speed of the boat in still water is 'w' Speed of the current is 'c' Let the distance between two places is 'd' According to the question, motorboat takes half time to cover a certain distance downstream than upstream. d w + c = 1 2 d w - c => 2w - 2c = w + c => w = 3c => c : w = 1 : 3 Hence, the ratio between rate of current(c) and rate of boat in still water(w) = 1 : 3

Question 11

A man can row upstream at 16 km/hr and downstream at 24 km/hr. Find the speed of the current.

Accepted Answer

Speed of the current = 24-16/2 = 8/2 = 4 km/hr.

Question 12

A motorboat goes 8 km an hour in still water, but takes thrice as much time in going the same distance against the current than going with the current. Then find the speed of the current?

Accepted Answer

Let the speed of current = 'C' km/hr Given the speed of boat in still water = 6 kmph Let 'd' kms be the distance it covers. According to the given data, Boat takes thrice as much time in going the same distance against the current than going with the current i.e, d 8 - C = 3 × d 8 + C ⇒ 24 - 3 C = 8 + C ⇒ 4 C = 16 ⇒ C = 4 kmph Hence, the speed of the current C = 4 kmph.

Question 13

A boat while travelling upstream covers a distance of 29 km at the speed of 6 km/h, whereas while travelling downstream it covers the same distance at a speed of 12 km/h. What is the speed of the boat in still water?

Accepted Answer

Speed of boat in still water = 1/2 (12 + 6) = 9 kmph.

Question 14

If the boat goes 7 kms upstream in 42 min and speed of the stream is 3 kmph, then the speed of the boat in still water ?

Accepted Answer

Given that, upstream distance = 7 kms Upstream speed = 7/42 x 60 = 10 kms Speed of the stream = 3 kmph Let speed in still water = M kmph, then Upstream speed = M - 3 = 10 => M = 13 kmph.

Question 15

A boat goes 4 km upstream and 4 km downstream in 1 hour. The same boat goes 5 km downstream and 3 km upstream in 55 minutes. What is the speed (in km/hr) of oat in still water?

Accepted Answer

9

Question 16

A boat travels 24 km upstream in 6 h and 20 km downstream in 4 h. then, the speed of a boat in still water and the speed of current are respectively

Accepted Answer

Distance travelled by boat in upstream=24km Time taken = 6 h Speed of the boat in upstream = 24/6 = 4 km/h And distance travelled by boat in downstream = 20 km Time taken = 4h Speed of the boat in downstream = 20/4 km/h = 5 km/h Now, speed of the boat in still water = 1/2 [ speed of the boat in upstream + speed of the boat in downstream] =1/2 [4 + 5] = 1/2 × 9 = 4.5 km/h And speed of the current = 1⁄2 [speed of the boat in downstream – speed of the boat in upstream] = 1/2 [5 – 4] = 1/2 × 1 = 0.5 km/h

Question 17

Mahesh rows to the place 80 km away and back in 20 hours. He finds that he can row 8 km downstream in the same time as 4 km upstream. The speed of the boat in stillwater is

Accepted Answer

If Mahesh moves 8 km downstream in X hours Downstream speed = 8/X kmph upstream speed = 4/X kmph Now 80/(8/X) + 80/(4/X)=20 X=2/3 downstream Speed = 8/(2/3)= 12 kmph upstream Speed = 4/(2/3)= 6 kmph Rate of the stream = (12+6)/2= 9 kmph

Question 18

Equal distance is covered by a boat in upstream and in downstream in total 5 hours. Sum of speed of a boat in upstream and downstream is 40 km/hr. Speed of boat in still water is 600% more than the speed of stream. Find theapproximate distance cover…

Accepted Answer

let speed of boat= X, speed of stream= Y Upstream speed= X-Y Downstream speed= X+Y Sum of upstream & downstream= (X-Y) +(X+Y)= 2X So, 2X= 40 X= 20 km/hr Speed of boat : speed of stream= 600+100 :100= 7:1 So speed of Stream= 20/7 km/hr ATQ, D/( X-Y) + D/( X+Y) = 5 D/(120/7) + D/(160/7)= 5 D= 480×5/49= 48.97 km= 50 Km(approx)

Question 19

A boat takes 2 hours to travel from point A to B in still water. To find out its speed upstream, which of the following information is/are required? A. Distance between point A and B. B. Time taken to travel downstream from B to A. C. Speed of the s…

Accepted Answer

Let distance between A & B = d km Let speed in still water = x kmph Let speed of current = y kmph from the given data, d/x = 2 From A) we get d From B) we get d/x+y From C) we get y So, Any one pair of A and B, B and C or C and A is sufficient to give the answer i.e, the speed of upstream.

Question 20

Choose the most appropriate answer:A boat travels upstream from B to A and downstream from A to B in 3 hours. If the speed of the boat in still water is 9 Km/h and the speed of the current is 3 Km/h, the distance between A and B is

Accepted Answer

Speed of boat in still water = 9 km/hr Speed of current = 3km/hr Downstream speed = 9+3 = 12 km/hr Upstream speed = 9-3 =6 km/hr Let the distance between A to B be x km. x/6 + x/12 = 3x + 2x = 36 3x = 36 x = 12 km

Boats and Streams Questions