Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 2)
2.
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:
Answer: Option
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.
Discussion:
72 comments Page 5 of 8.
Atuljain said:
1 decade ago
Downstream = speed of the man + speed of the stream.
15 = x+2.5.
x = 12.5.
Upstream = speed of the man - speed of the stream.
x = 12.5-2.5.
x = 10.
15 = x+2.5.
x = 12.5.
Upstream = speed of the man - speed of the stream.
x = 12.5-2.5.
x = 10.
Karthik said:
1 decade ago
The actual speed is 12.5. Due to downstream it becomes 15 (adding 2.5) and due to upstream it becomes 10 (subtracting 2.5). Simple no confusions.
Sapna said:
1 decade ago
Solve acc to formula,
We have
Current=1/2(a-b).
So,
2.5=1/2(15-b).
2.5*2=15-b.
b=10km/hr.
We have
Current=1/2(a-b).
So,
2.5=1/2(15-b).
2.5*2=15-b.
b=10km/hr.
Raj said:
1 decade ago
The speed of man is 15 including the speed of current.
Actual speed of man is 12. 5,
And now against the current 12. 5-2. 5 (speed of current) =10.
Actual speed of man is 12. 5,
And now against the current 12. 5-2. 5 (speed of current) =10.
Prasad said:
1 decade ago
How do we know the man is traveling in boat with out mention in the question?
Suraj said:
1 decade ago
Thanks balaji.
Vijaya said:
1 decade ago
Hi. Guyz. I have one doubt. ? how we know. The given question is upstream or downstream. I can't understand that. If you don't mind can you please tell me that.
Hitesh bulani said:
1 decade ago
Thanku balaji.
Anup gupta said:
1 decade ago
No upstream speed can be any one less than 12.5. I. E. Against the stream. Question is not that what will be the speed if he will move against the stream at 2.5.
Sravya said:
1 decade ago
Let speed of man be 'a'
speed of current be 'b'
given man's speed with current (a+b)=15 km\hr nd speed of current is 2.5
substitute in abv eqn (a+2.5)=15
a=15-2.5
a=12.5
but problem is abt finding man's speed against current i,e
(a-b)=12.5-2.5
=10
speed of current be 'b'
given man's speed with current (a+b)=15 km\hr nd speed of current is 2.5
substitute in abv eqn (a+2.5)=15
a=15-2.5
a=12.5
but problem is abt finding man's speed against current i,e
(a-b)=12.5-2.5
=10
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