Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 3)
3.
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?
Answer: Option
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.
Discussion:
109 comments Page 8 of 11.
Prahadee said:
1 decade ago
I don't understand the ratio. Can anyone explain me?
Ganesha (lecturer) said:
1 decade ago
You are excellent @Aparna, @Mady you too. Both are right is solving this but we have to go still easier and a shortcut method to solve why because is we can't waste 10 mins for a single aptitude in the examinations, which may lead to shortage of time.
Great job appreciative but still try best don't settle for good.
Great job appreciative but still try best don't settle for good.
Arjun said:
1 decade ago
@Jessie.
The stream of the boat is also influenced by the flow of the current, and moreover given here is with the relationship of the boat speed with the current.
The stream of the boat is also influenced by the flow of the current, and moreover given here is with the relationship of the boat speed with the current.
Jessie said:
1 decade ago
How does the upstream:downstream relates the ratio speed of the boat:speed of the water current as asked in question?
Mady said:
1 decade ago
Boat Speed In still water = u.
Stream Speed = v.
DS = u+v US = u-v.
Distance = (u+v)4 = (u-v)44/5 (rough : 8*48/60= 44/5).
so (u+v) = (u-v)11/5 (rough : canceled 4 & 44.. 11 times).
5(u+v) = (u-v)11.
5u+5v = 11u-11v.
5u-11u = -11v-5v.
-6u = -16v.
u/v = 16/6= 8/3 .
So 8:3.
Stream Speed = v.
DS = u+v US = u-v.
Distance = (u+v)4 = (u-v)44/5 (rough : 8*48/60= 44/5).
so (u+v) = (u-v)11/5 (rough : canceled 4 & 44.. 11 times).
5(u+v) = (u-v)11.
5u+5v = 11u-11v.
5u-11u = -11v-5v.
-6u = -16v.
u/v = 16/6= 8/3 .
So 8:3.
Aparna said:
1 decade ago
We all know this basic rule of finding ratio which is:
x/y = a/b.
Further when we solve this, we get:
x+y/x-y = a+b/a-b .... equation (1).
Solution:
Let the boat's speed upstream be x & downstream be y.
Therefore,
According to the formula, Distance = Speed*Time.
We get for upstream, D= x*44/5.
& for downstream, D= x*4.
Now, in the question, it is given that the distance covered is same while going upstream and downstream.
Therefore,
x*44/5 = 4y.
x/y = 11/5 (satisfies the equation: x/y = a/b).
Now put this value of x/y in equation (1).
x+y/x-y = 11+5/11-5.
x+y/x-y = 16/6.
x+y/x-y = 8/3.
8:3 is the Answer.
x/y = a/b.
Further when we solve this, we get:
x+y/x-y = a+b/a-b .... equation (1).
Solution:
Let the boat's speed upstream be x & downstream be y.
Therefore,
According to the formula, Distance = Speed*Time.
We get for upstream, D= x*44/5.
& for downstream, D= x*4.
Now, in the question, it is given that the distance covered is same while going upstream and downstream.
Therefore,
x*44/5 = 4y.
x/y = 11/5 (satisfies the equation: x/y = a/b).
Now put this value of x/y in equation (1).
x+y/x-y = 11+5/11-5.
x+y/x-y = 16/6.
x+y/x-y = 8/3.
8:3 is the Answer.
SUJISHNU ADHYA said:
1 decade ago
An easy way to solve.
Let speed of boat and water be x km/hr and y km/hr respectively.
Upstream = x-y km/hr.
Downstream = x+y km/hr.
ATQ,
[8+(48/60)](x-y) = 4(x+y)(SINCE DISTANCE IS EQUAL).
8+4/5(x-y) = 4x + 4y.
44/5 x - 44/5 y= 4x + 4y.
44/5x - 4x = 4y + 44/5 y.
24x = 64 y.
x/y = 64/24.
x/y = 16 / 6.
x/y = 8 / 3 (answer).
Let speed of boat and water be x km/hr and y km/hr respectively.
Upstream = x-y km/hr.
Downstream = x+y km/hr.
ATQ,
[8+(48/60)](x-y) = 4(x+y)(SINCE DISTANCE IS EQUAL).
8+4/5(x-y) = 4x + 4y.
44/5 x - 44/5 y= 4x + 4y.
44/5x - 4x = 4y + 44/5 y.
24x = 64 y.
x/y = 64/24.
x/y = 16 / 6.
x/y = 8 / 3 (answer).
Papesh roul said:
1 decade ago
Let the speed of the Boat be: a kmph and Speed of the stream be: b kmph.
Distance =44/5 * (a-b) = 4 * (a+b).
By this equation we will get a/b = 8:3.
Distance =44/5 * (a-b) = 4 * (a+b).
By this equation we will get a/b = 8:3.
Vikas verma said:
1 decade ago
Let the speed of the Boat be X kmph and Speed of the stream be Y kmph.
Then 44/5 * (X-Y) = 4 * (X+Y).
By solving the equation you will get X/Y = 8:3.
I hope you'll understand.
Then 44/5 * (X-Y) = 4 * (X+Y).
By solving the equation you will get X/Y = 8:3.
I hope you'll understand.
(1)
Raju said:
1 decade ago
I want to know how these equation is done?
16x/5 and 6x/5.
16x/5 and 6x/5.
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