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Boats and Streams Aptitude Questions and Answers:
Here i am going to provide you problems on boats and streams for SSC Exam,boat and stream Question and Answer for Bank Po, Percentage Question and Answer Lic exam. simply candidate can register and take online Quiz. Jobriya.co.in going to share with you boat and stream formula, boats and streams tricks,boats and streams shortcuts,percentage question and answers.in this chapter you know how you can solve percentage problems within second . here i am going to share percentage tricks,boats and streams shortcuts with example after that we provide boats and streams online quiz.
Boat and Stream Formula:
 Speed of the boat against stream or while moving upstream = Speed of the boat in still water – Speed of the stream.
 Speed of the boat with stream or while moving downstream= Speed of the boat in still water + Speed of the Stream.
 If ‘p’ is the speed of the boat down the stream and ‘q’ is the speed of the boat up the stream, then,
 Speed of the boat in still water = (p+q) / 2.
 Speed of the boat of the water stream = (pq) / 2.
 These problems are governed by the following results: Downstream (along the current) speed (D) = Boat speed (B) + current (stream) speed (C). D=B+C
Upstream (against the current) speed (U) = Boat speed – current (stream) speed. U=B–C
Speed of the boat = average of downstream and upstream speeds B = (D + U)/2
Speed of the current = half the difference of downstream and upstream speeds C = (D – U)/2
Boat and Stream Short Cuts
Boat and Stream Short Tricks 1: Given a boat travels downstream with speed d km/hr and it travels with speed ukm/hr upstream. Find the speed of stream and speed of boat in still water.
Let speed of boat in still water be bkm/hr and speed of stream be skm/hr.
Then b + s = d and b – s = u.
Solving the 2 equations we get,
b = (d + u)/2
s = (d – u)/2
Boat and Stream Short Tricks 2: A man can row a boat, certain distance downstream in td hours and returns the same distance upstream in tu hours. If the speed of stream is s km/h, then the speed of boat in still water is given by
We know distance = speed * time
Let the speed of boat be b km/hr
Case downstream:
d = (b + s) * td
Case upstream:
d = (b – s) * tu
=> (b + s) / (b – s) = tu / td
b = [(tu + td) / (tu – td)] * s
Boat and Stream Short Tricks 3: A man can row in still water at b km/h. In a stream flowing at s km/h, if it takes him t hours to row to a place and come back, then the distance between two places, d is given by
Downstream: Let the time taken to go downstream be td
d = (b + s) * td
Upstream: Let the time taken to go upstream be tu
d = (b – s) * tu
td + tu = t
[d / (b + s)] + [d / (b – s)] = t
So, d = t * [(b^{2} – s^{2}) / 2b]
OR
d = [t * (Speed to go downstream) * (Speed to go upstream)]/[2 * Speed of boat or man in still water]
Boat and Stream Short Tricks 4: A man can row in still water at b km/h. In a stream flowing at s km/h, if it takes t hours more in upstream than to go downstream for the same distance, then the distance d is given by
Time taken to go upstream = t + Time taken to go downstream
(d / (b – s)) = t + (d / (b + s))
=> d [ 2s / (b^{2} – s^{2} ] = t
So, d = t * [(b^{2} – s^{2}) / 2s]
OR
d = [t * (Speed to go downstream) * (Speed to go upstream)] / [2 * Speed of still water]
Example:
Boat Stream Solved Problem
Sol. Rate in still water=1/2(10+7)km/hr=8.5 km/hr.
Rate of current=1/2(107)km/hr=1.5 km/hr.
Sol. rate downstream=(15/3 ¾)km/hr=(15*4/15)km/hr=4km/hr.
Rate upstream=(5/2 ½)km/hr=(5*2/5)km/hr=2km/hr.
Speed of current=1/2(42)km/hr=1km/hr
Sol. Let man’s rate upstream be x kmph.then ,his rate downstream=3xkmph.
So,2x=18 or x=9.
Rate upstream=9 km/hr,rate downstream=27 km/hr.
Hence,rate of stream=1/2(279)km/hr=9 km/hr.
Sol. Clearly the cyclist moves both ways at a speed of 12 km/hr.
The boat sailor moves downstream @ (10+4)i.e.,14 km/hr and upstream @ (104)i.e.,
6km/hr.
So,average speed of the boat sailor=(2*14*6/14+6)km/hr
=42/5 km/hr=8.4 km/hr.
since the average speed of the cyclist is greater ,he will return ta A first.
Sol. Speed downstream =(7.5+1.5)km/hr=9 km/hr;
Speed upstream=(7.51.5)kmph=6kmph.
Let the required distance be x km.then,
x/9+x/6=50/60.
2x+3x=(5/6*18)
5x=15
x=3.
Hence,the required distance is 3km.
Sol.let the speed of the motarboat in still water be x kmph.then,
6/x+2 +6/x2=33/60
11×2240x44=0
11×2242x+2x44=0
(x22)(11x+2)=0
x=22.
Sol.let rate upstream=x km/hr and rate downstream=y km/hr.
Then,40/x +55/y =13…(i) and 30/x +44/y =10
Multiplying (ii) by 4 and (i) by 3 and subtracting ,we get:11/y=1 or y=11.
Substituting y=11 in (i),we get:x=5.
Rate in still water =1/2(11+5)kmph=8kmph.
Rate of current=1/2(115)kmph=3kmph
Boat and stream Quiz
Boats and Streams Questions Answers
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Question 1 of 30
1. Question
A man can row upstream 10 kmph and downstream 20 kmph. Find the man rate in still water and rate of the stream.
Correct
Please remember,
If a is rate downstream and b is rate upstream
Rate in still water = 1/2(a+b)
Rate of current = 1/2(ab)=> Rate in still water = 1/2(20+10) = 15 kmph
=> Rate of current = 1/2(2010) = 5 kmphIncorrect
Please remember,
If a is rate downstream and b is rate upstream
Rate in still water = 1/2(a+b)
Rate of current = 1/2(ab)=> Rate in still water = 1/2(20+10) = 15 kmph
=> Rate of current = 1/2(2010) = 5 kmph 
Question 2 of 30
2. Question
man takes 3 hours 45 minutes to row a boat 15 km downstream of a river and 2 hours 30 minutes to cover a distance of 5 km upstream. Find the speed of the current.
Correct
Explanation:
First of all, we know that
speed of current = 1/2(speed downstream – speed upstream) [important]So we need to calculate speed downstream and speed upstream first.
Speed = Distance / Time [important]
Speed upstream =(15334)km/hr=15×415=4km/hrSpeed Downstream = (5212)km/hr=5×25=2km/hrSo speed of current = 12(4−2)=1km/hrSpeed upstream =(15334)km/hr=15×415=4km/hrSpeed Downstream = (5212)km/hr=5×25=2km/hrSo speed of current = 12(4−2)=1km/hr
Incorrect
Explanation:
First of all, we know that
speed of current = 1/2(speed downstream – speed upstream) [important]So we need to calculate speed downstream and speed upstream first.
Speed = Distance / Time [important]
Speed upstream =(15334)km/hr=15×415=4km/hrSpeed Downstream = (5212)km/hr=5×25=2km/hrSo speed of current = 12(4−2)=1km/hrSpeed upstream =(15334)km/hr=15×415=4km/hrSpeed Downstream = (5212)km/hr=5×25=2km/hrSo speed of current = 12(4−2)=1km/hr

Question 3 of 30
3. Question
In one hour, a boat goes 11km along the stream and 5 km against it. Find the speed of the boat in still water
Correct
Explanation:
We know we can calculate it by 1/2(a+b)=> 1/2(11+5) = 1/2(16) = 8 km/hr
Incorrect
Explanation:
We know we can calculate it by 1/2(a+b)=> 1/2(11+5) = 1/2(16) = 8 km/hr

Question 4 of 30
4. Question
A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is
Correct
Let the speed of the stream be x km/hr. Then,
Speed downstream = (15 + x) km/hr,
Speed upstream = (15 – x) km/hrSo we know from question that it took 4(1/2)hrs to travel back to same point.
So,
3015+x−3015−x=412=>900225−x2=92=>9×2=225=>x=5km/hr3015+x−3015−x=412=>900225−x2=92=>9×2=225=>x=5km/hr
Incorrect
Let the speed of the stream be x km/hr. Then,
Speed downstream = (15 + x) km/hr,
Speed upstream = (15 – x) km/hrSo we know from question that it took 4(1/2)hrs to travel back to same point.
So,
3015+x−3015−x=412=>900225−x2=92=>9×2=225=>x=5km/hr3015+x−3015−x=412=>900225−x2=92=>9×2=225=>x=5km/hr

Question 5 of 30
5. Question
If Rahul rows 15 km upstream in 3 hours and 21 km downstream in 3 hours, then the speed of the stream is
Correct
Rate upstream = (15/3) kmph
Rate downstream (21/3) kmph = 7 kmph.
Speed of stream (1/2)(7 – 5)kmph = 1 kmphIncorrect
Rate upstream = (15/3) kmph
Rate downstream (21/3) kmph = 7 kmph.
Speed of stream (1/2)(7 – 5)kmph = 1 kmph 
Question 6 of 30
6. Question
A man rows 750 m in 675 seconds against the stream and returns in 7 and half minutes. His rowing speed in still water is
Correct
Explanation:
Rate upstream = (750/675) = 10/9 m/sec
Rate downstream (750/450) m/sec = 5/3 m/sec
Rate in still water = (1/2)*[(10/9) + (5/3)] m/sec.
= 25/18 m/sec
= (25/18)*(18/5) kmph
= 5 kmphIncorrect
Explanation:
Rate upstream = (750/675) = 10/9 m/sec
Rate downstream (750/450) m/sec = 5/3 m/sec
Rate in still water = (1/2)*[(10/9) + (5/3)] m/sec.
= 25/18 m/sec
= (25/18)*(18/5) kmph
= 5 kmph 
Question 7 of 30
7. Question
If a boat goes 7 km upstream in 42 minutes and the speed of the stream is 3 kmph, then the speed of the boat in still water is
Correct
Explanation:
Rate upstream = (7/42)*60 kmh = 10 kmph.
Speed of stream = 3 kmph.
Let speed in sttil water is x km/hr
Then, speed upstream = (x —3) km/hr.
x3 = 10 or x = 13 kmphIncorrect
Explanation:
Rate upstream = (7/42)*60 kmh = 10 kmph.
Speed of stream = 3 kmph.
Let speed in sttil water is x km/hr
Then, speed upstream = (x —3) km/hr.
x3 = 10 or x = 13 kmph 
Question 8 of 30
8. Question
A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat in still water and stream is
Correct
Explanation:
Let speed downstream = x kmph
Then Speed upstream = 2x kmphSo ratio will be,
(2x+x)/2 : (2xx)/2
=> 3x/2 : x/2 => 3:1Incorrect
Explanation:
Let speed downstream = x kmph
Then Speed upstream = 2x kmphSo ratio will be,
(2x+x)/2 : (2xx)/2
=> 3x/2 : x/2 => 3:1 
Question 9 of 30
9. Question
A man’s speed with the current is 20 kmph and speed of the current is 3 kmph. The Man’s speed against the current will be
Correct
Explanation:
If you solved this question yourself, then trust me you have a all very clear with the basics of this chapter.If not then lets solve this together.
Speed with current is 20,
speed of the man + It is speed of the current
Speed in still water = 20 – 3 = 17Now speed against the current will be
speed of the man – speed of the current
= 17 – 3 = 14 kmphIncorrect
Explanation:
If you solved this question yourself, then trust me you have a all very clear with the basics of this chapter.If not then lets solve this together.
Speed with current is 20,
speed of the man + It is speed of the current
Speed in still water = 20 – 3 = 17Now speed against the current will be
speed of the man – speed of the current
= 17 – 3 = 14 kmph 
Question 10 of 30
10. Question
A boat can travel with a speed of 16 km/hr in still water. If the rate of stream is 5 km/hr, then find the time taken by the boat to cover distance of 84 km downstream.
Correct
Explanation:
It is very important to check, if the boat speed given is in still water or with water or against water. Because if we neglect it we will not reach on right answer. I just mentioned here because mostly mistakes in this chapter are of this kind only.Lets see the question now.
Speed downstream = (16 + 5) = 21 kmphTime = distance/speed = 84/21 = 4 hours
Incorrect
Explanation:
It is very important to check, if the boat speed given is in still water or with water or against water. Because if we neglect it we will not reach on right answer. I just mentioned here because mostly mistakes in this chapter are of this kind only.Lets see the question now.
Speed downstream = (16 + 5) = 21 kmphTime = distance/speed = 84/21 = 4 hours

Question 11 of 30
11. Question
A man can row at 5 kmph in still water. If the velocity of the current is 1 kmph and it takes him 1 hour to row to a place and come back. how far is that place.
Correct
Explanation:
Let the distance is x km
Rate downstream = 5 + 1 = 6 kmph
Rate upstream = 5 – 1 = 4 kmph
then
x/6 + x/4 = 1 [because distance/speed = time]
=> 2x + 3x = 12
=> x = 12/5 = 2.4 kmIncorrect
Explanation:
Let the distance is x km
Rate downstream = 5 + 1 = 6 kmph
Rate upstream = 5 – 1 = 4 kmph
then
x/6 + x/4 = 1 [because distance/speed = time]
=> 2x + 3x = 12
=> x = 12/5 = 2.4 km 
Question 12 of 30
12. Question
The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is
Correct
Answer: Option C
Explanation:
Speed downstreams=(15 + 3)kmph
= 18 kmph.
Distance travelled = (18 x 12/60)km
= 3.6kmIncorrect
Answer: Option C
Explanation:
Speed downstreams=(15 + 3)kmph
= 18 kmph.
Distance travelled = (18 x 12/60)km
= 3.6km 
Question 13 of 30
13. Question
A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream.
Correct
Explanation:
Speed downstream = (13 + 4) km/hr = 17 km/hr.
Time taken to travel 68 km downstream = 68 hrs = 4 hrs. 17 Incorrect
Explanation:
Speed downstream = (13 + 4) km/hr = 17 km/hr.
Time taken to travel 68 km downstream = 68 hrs = 4 hrs. 17 
Question 14 of 30
14. Question
A man’s speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man’s speed against the current is:
Correct
Explanation:
Man’s rate in still water = (15 – 2.5) km/hr = 12.5 km/hr.
Man’s rate against the current = (12.5 – 2.5) km/hr = 10 km/hr.
Incorrect
Explanation:
Man’s rate in still water = (15 – 2.5) km/hr = 12.5 km/hr.
Man’s rate against the current = (12.5 – 2.5) km/hr = 10 km/hr.

Question 15 of 30
15. Question
A boat 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 boat and speed of the water current respectively
Correct
Explanation:
Let the man’s rate upstream be x kmph and that downstream be y kmph.
Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs.
x x 8 4 = (y x 4) 5 44 x =4y 5 y = 11 x. 5 Required ratio = y + x : y – x 2 2 = 16x x 1 : 6x x 1 5 2 5 2 = 8 : 3 5 5 = 8 : 3.
Incorrect
Explanation:
Let the man’s rate upstream be x kmph and that downstream be y kmph.
Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs.
x x 8 4 = (y x 4) 5 44 x =4y 5 y = 11 x. 5 Required ratio = y + x : y – x 2 2 = 16x x 1 : 6x x 1 5 2 5 2 = 8 : 3 5 5 = 8 : 3.

Question 16 of 30
16. Question
A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is: Correct
Explanation:
Let the speed of the stream be x km/hr. Then,
Speed downstream = (15 + x) km/hr,
Speed upstream = (15 – x) km/hr.
30 + 30 = 4 1 (15 + x) (15 – x) 2 900 = 9 225 – x^{2} 2 9x^{2} = 225
x^{2} = 25
x = 5 km/hr
Incorrect
Explanation:
Let the speed of the stream be x km/hr. Then,
Speed downstream = (15 + x) km/hr,
Speed upstream = (15 – x) km/hr.
30 + 30 = 4 1 (15 + x) (15 – x) 2 900 = 9 225 – x^{2} 2 9x^{2} = 225
x^{2} = 25
x = 5 km/hr

Question 17 of 30
17. Question
In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is: Correct
Explanation:
Speed in still water = 1 (11 + 5) kmph = 8 kmph. 2 Incorrect
Explanation:
Speed in still water = 1 (11 + 5) kmph = 8 kmph. 2 
Question 18 of 30
18. Question
A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water?
Correct
Explanation:
Rate downstream = 16 kmph = 8 kmph. 2 Rate upstream = 16 kmph = 4 kmph. 4 Speed in still water = 1 (8 + 4) kmph = 6 kmph. 2 Incorrect
Explanation:
Rate downstream = 16 kmph = 8 kmph. 2 Rate upstream = 16 kmph = 4 kmph. 4 Speed in still water = 1 (8 + 4) kmph = 6 kmph. 2 
Question 19 of 30
19. Question
The speed of a boat in still water in 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is:
Correct
Explanation:
Speed downstream = (15 + 3) kmph = 18 kmph.
Distance travelled = 18 x 12 km = 3.6 km. 60 Incorrect
Explanation:
Speed downstream = (15 + 3) kmph = 18 kmph.
Distance travelled = 18 x 12 km = 3.6 km. 60 
Question 20 of 30
20. Question
A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is:
Correct
Explanation:
Let the speed of the stream x mph. Then,
Speed downstream = (10 + x) mph,
Speed upstream = (10 – x) mph.
36 – 36 = 90 (10 – x) (10 + x) 60 72x x 60 = 90 (100 – x^{2})
x^{2} + 48x – 100 = 0
(x+ 50)(x – 2) = 0
x = 2 mph.
Incorrect
Explanation:
Let the speed of the stream x mph. Then,
Speed downstream = (10 + x) mph,
Speed upstream = (10 – x) mph.
36 – 36 = 90 (10 – x) (10 + x) 60 72x x 60 = 90 (100 – x^{2})
x^{2} + 48x – 100 = 0
(x+ 50)(x – 2) = 0
x = 2 mph.

Question 21 of 30
21. Question
A man can row at 5 kmph in still water. If the velocity of current is 1 kmph and it takes him 1 hour to row to a place and come back, how far is the place?
Correct
Explanation:
Speed downstream = (5 + 1) kmph = 6 kmph.
Speed upstream = (5 – 1) kmph = 4 kmph.
Let the required distance be x km.
Then, x + x = 1 6 4 2x + 3x = 12
5x = 12
x = 2.4 km.
Incorrect
Explanation:
Speed downstream = (5 + 1) kmph = 6 kmph.
Speed upstream = (5 – 1) kmph = 4 kmph.
Let the required distance be x km.
Then, x + x = 1 6 4 2x + 3x = 12
5x = 12
x = 2.4 km.

Question 22 of 30
22. Question
A boat covers a certain distance downstream in 1 hour, while it comes back in 1 hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?
Correct
Explanation:
Let the speed of the boat in still water be x kmph. Then,
Speed downstream = (x + 3) kmph,
Speed upstream = (x – 3) kmph.
(x + 3) x 1 = (x – 3) x 3 2 2x + 6 = 3x – 9
x = 15 kmph.
Incorrect
Explanation:
Let the speed of the boat in still water be x kmph. Then,
Speed downstream = (x + 3) kmph,
Speed upstream = (x – 3) kmph.
(x + 3) x 1 = (x – 3) x 3 2 2x + 6 = 3x – 9
x = 15 kmph.

Question 23 of 30
23. Question
A boatman goes 2 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 5 km in stationary water? Correct
Explanation:
Rate downstream = 1 x 60 km/hr = 6 km/hr. 10 Rate upstream = 2 km/hr.
Speed in still water = 1 (6 + 2) km/hr = 4 km/hr. 2 Required time = 5 hrs = 1 1 hrs = 1 hr 15 min. 4 4 Incorrect
Explanation:
Rate downstream = 1 x 60 km/hr = 6 km/hr. 10 Rate upstream = 2 km/hr.
Speed in still water = 1 (6 + 2) km/hr = 4 km/hr. 2 Required time = 5 hrs = 1 1 hrs = 1 hr 15 min. 4 4 
Question 24 of 30
24. Question
A man can row threequarters of a kilometre against the stream in 11 minutes and down the stream in 7 minutes. The speed (in km/hr) of the man in still water is: Correct
Incorrect

Question 25 of 30
25. Question
Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is:
Correct
Explanation:
Speed upstream = 7.5 kmph.
Speed downstream = 10.5 kmph.
Total time taken = 105 + 105 hours = 24 hours. 7.5 10.5 Incorrect
Explanation:
Speed upstream = 7.5 kmph.
Speed downstream = 10.5 kmph.
Total time taken = 105 + 105 hours = 24 hours. 7.5 10.5 
Question 26 of 30
26. Question
A man takes twice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat (in still water) and the stream is: Correct
Explanation:
Let man’s rate upstream be x kmph.
Then, his rate downstream = 2x kmph.
(Speed in still water) : (Speed of stream) = 2x + x : 2x – x 2 2 = 3x : x 2 2 = 3 : 1.
Incorrect
Explanation:
Let man’s rate upstream be x kmph.
Then, his rate downstream = 2x kmph.
(Speed in still water) : (Speed of stream) = 2x + x : 2x – x 2 2 = 3x : x 2 2 = 3 : 1.

Question 27 of 30
27. Question
A man rows to a place 48 km distant and come back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is:
Correct
Explanation:
Suppose he move 4 km downstream in x hours. Then,
Speed downstream = 4 km/hr. x Speed upstream = 3 km/hr. x 48 + 48 = 14 or x = 1 . (4/x) (3/x) 2 So, Speed downstream = 8 km/hr, Speed upstream = 6 km/hr.
Rate of the stream = 1 (8 – 6) km/hr = 1 km/hr. 2 Incorrect
Explanation:
Suppose he move 4 km downstream in x hours. Then,
Speed downstream = 4 km/hr. x Speed upstream = 3 km/hr. x 48 + 48 = 14 or x = 1 . (4/x) (3/x) 2 So, Speed downstream = 8 km/hr, Speed upstream = 6 km/hr.
Rate of the stream = 1 (8 – 6) km/hr = 1 km/hr. 2 
Question 28 of 30
28. Question
A boat takes 38 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 4 kmph and the speed of the boat in still water is 14 kmph, what is the distance between A and B?
Correct
Explanation:
velocity of the stream = 4 kmph
Speed of the boat in still water is 14 kmphSpeed downstream = (14+4) = 18 kmph
Speed upstream = (144) = 10 kmphLet the distance between A and B be xx km
Time taken to travel downstream from A to B + Time taken to travel upstream from B to C(mid of A and B) = 38 hours
⇒x18+(x2)10=38 ⇒x18+x20=38 ⇒19x180=38 ⇒x180=2 ⇒x=360⇒x18+(x2)10=38 ⇒x18+x20=38 ⇒19×180=38 ⇒x180=2 ⇒x=360i.e., distance between A and B = 360 km
Incorrect
Explanation:
velocity of the stream = 4 kmph
Speed of the boat in still water is 14 kmphSpeed downstream = (14+4) = 18 kmph
Speed upstream = (144) = 10 kmphLet the distance between A and B be xx km
Time taken to travel downstream from A to B + Time taken to travel upstream from B to C(mid of A and B) = 38 hours
⇒x18+(x2)10=38 ⇒x18+x20=38 ⇒19x180=38 ⇒x180=2 ⇒x=360⇒x18+(x2)10=38 ⇒x18+x20=38 ⇒19×180=38 ⇒x180=2 ⇒x=360i.e., distance between A and B = 360 km

Question 29 of 30
29. Question
The speed of a boat in still water is 10 km/hr. If it can travel 78 km downstream and 42 km upstream in the same time, the speed of the stream is
Correct
Explanation:
Let the speed of the stream be xx km/hr. Then
Speed upstream =(10−x)=(10−x) km/hr
Speed downstream =(10+x)=(10+x) km/hrTime taken to travel 78 km downstream = Time taken to travel 42 km upstream
⇒7810+x=4210−x ⇒2610+x=1410−x ⇒1310+x=710−x ⇒130−13x=70+7x ⇒20x=60 ⇒x=3 km/hrIncorrect
Explanation:
Let the speed of the stream be xx km/hr. Then
Speed upstream =(10−x)=(10−x) km/hr
Speed downstream =(10+x)=(10+x) km/hrTime taken to travel 78 km downstream = Time taken to travel 42 km upstream
⇒7810+x=4210−x ⇒2610+x=1410−x ⇒1310+x=710−x ⇒130−13x=70+7x ⇒20x=60 ⇒x=3 km/hr 
Question 30 of 30
30. Question
A man can row 40 kmph in still water and the river is running at 10 kmph. If the man takes 1 hr to row to a place and back, how far is the place?
Correct
Explanation:
Let the distance be xx
Speed upstream = (40 – 10) = 30 kmph
Speed downstream = (40 + 10) = 50 kmphTotal time taken = 1 hr
⇒x50+x30=1⇒8x150=1⇒x=1508= 18.75 kmIncorrect
Explanation:
Let the distance be xx
Speed upstream = (40 – 10) = 30 kmph
Speed downstream = (40 + 10) = 50 kmphTotal time taken = 1 hr
⇒x50+x30=1⇒8x150=1⇒x=1508= 18.75 km