21) 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
- 1) 11 kmph
- 2) 12 kmph
- 3) 14 kmph
- 4) 17 kmph
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View Explanation
Ans. C
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 = 17
Now speed against the current will be
speed of the man - speed of the current
= 17 - 3 = 14 kmph
22) 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 downstre
- 1) 4 hours
- 2) 5 hours
- 3) 6 hours
- 4) 7 hours
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View Explanation
Ans. A
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 kmph
Time = distance/speed = 84/21 = 4 hours
23) 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
- 1) 3:1
- 2) 1:3
- 3) 2:4
- 4) 4:2
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View Explanation
Ans. A
Explanation :
Let speed downstream = x kmph
Then Speed upstream = 2x kmph
So ratio will be,
(2x+x)/2 : (2x-x)/2
=> 3x/2 : x/2 => 3:1
24) 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 pla
- 1) .4 km
- 2) 1.4 km
- 3) 2.4 km
- 4) 3.4 km
View Answer
View Explanation
Ans. C
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
25) 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
- 1) 1.6 km
- 2) 2 km
- 3) 3.6 km
- 4) 4 km
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View Explanation
Ans. C
Explanation :
Speed downstreams =(15 + 3)kmph
= 18 kmph.
Distance travelled = (18 x 12/60)km
= 3.6km
26) 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
- 1) 12 kmph
- 2) 13 kmph
- 3) 14 kmph
- 4) 15 kmph
View Answer
View Explanation
Ans. B
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 â€”3) km/hr.
x-3 = 10 or x = 13 kmph
27) 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
- 1) 3:1
- 2) 1:3
- 3) 2:4
- 4) 4:2
View Answer
View Explanation
Ans. A
Explanation :
Let speed downstream = x kmph
Then Speed upstream = 2x kmph
So ratio will be,
(2x+x)/2 : (2x-x)/2
=> 3x/2 : x/2 => 3:1
28) 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 downstre
- 1) 4 hours
- 2) 5 hours
- 3) 6 hours
- 4) 7 hours
View Answer
View Explanation
Ans. A
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 kmph
Time = distance/speed = 84/21 = 4 hours
29) 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
- 1) 11 kmph
- 2) 12 kmph
- 3) 14 kmph
- 4) 17 kmph
View Answer
View Explanation
Ans. C
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 = 17
Now speed against the current will be
speed of the man - speed of the current
= 17 - 3 = 14 kmph
30) 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 pla
- 1) .4 km
- 2) 1.4 km
- 3) 2.4 km
- 4) 3.4 km
View Answer
View Explanation
Ans. C
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