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 9 of 11.
Bhaskar said:
8 years ago
Explain me, why are we taking x=1 before 16x/5*1/2?
BHASKAR said:
8 years ago
Required ratio = (x+y)/2 : (x-y)/2 // here 2 is to take average.
Explain this.
Explain this.
Saransh said:
8 years ago
@Amit Lamba.
Thank you, it was easy to understand.
Thank you, it was easy to understand.
Vino said:
8 years ago
This method is easy to understand. Thank you @Hely.
Praveen kumar said:
8 years ago
I don't understand why the factor 1/2 comes at the last while calculating the speed of the boat in upstream and downstream { (x+y) /2: (x-y) /2}?
Sekhar said:
8 years ago
The speed of the boat = 1/2(up stream + downstream) speed of the current = 1/2(up stream - downstream).
converting 8 hours 48 minutes to minutes which is 528 minutes.
converting 4 hours to minutes which is 240 minutes.
1/2(528+240) : 1/2(528-240).
1/2 on both sides gets canceled so,
768 : 288 ==> 8: 3.
converting 8 hours 48 minutes to minutes which is 528 minutes.
converting 4 hours to minutes which is 240 minutes.
1/2(528+240) : 1/2(528-240).
1/2 on both sides gets canceled so,
768 : 288 ==> 8: 3.
Ramya said:
8 years ago
Could you please explain 2nd part of the answer (ratio) ?
Siddharth said:
8 years ago
It's very easy and understandable method. Thank you very much for this solution BINDU.
Manikandan said:
8 years ago
For required ratio:
The speed of boat:speed of current.
(u+v)/2 : (u-v)/2.
Here:y=11x/5 =u,
(11x/5+x)/2:(11x/5-x) //take LCM,
16x/5:6x/5,
16x:6x,
8:3.
The speed of boat:speed of current.
(u+v)/2 : (u-v)/2.
Here:y=11x/5 =u,
(11x/5+x)/2:(11x/5-x) //take LCM,
16x/5:6x/5,
16x:6x,
8:3.
Sriteja said:
8 years ago
@Sujishnu Adhya & @Binza.
Your explanation made me easy to understand. Thanks.
Your explanation made me easy to understand. Thanks.
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