Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 8)
8.
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:
Answer: Option
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 - x2)
x2 + 48x - 100 = 0
(x+ 50)(x - 2) = 0
x = 2 mph.
Discussion:
85 comments Page 6 of 9.
Aryan said:
7 years ago
Time taken by upstream is 90 minutes more then the time taken by downstream.
Rohit said:
10 years ago
Can anyone please explain me that how did you get 36/(10-x)-36/(10+x)?
Sriteja said:
8 years ago
Why have we done addition here instead of subtraction? Please explain.
Raj said:
9 years ago
@Venkat.
How
36=S/1.3
S= 2.
Explain this step.
How
36=S/1.3
S= 2.
Explain this step.
Naveen kumar said:
9 years ago
Super @Sowmya. Your explanation is an easy way to get the answer.
Anishghoshroy said:
1 decade ago
x2+48x-100.
= x2+50x-2x-100.
= x(x+50)-2(x+50).
= (x-2)(x+50).
= x2+50x-2x-100.
= x(x+50)-2(x+50).
= (x-2)(x+50).
Singh said:
3 years ago
Why you have subtracted 36/ (10-x) -36/ (36+x) ? Please explain.
(13)
Revathi said:
7 years ago
Why are we subtracting downstream and upstream? Please explain.
(1)
Sireesha said:
1 decade ago
The time difference between downstream and upstream is 90 min.
Keerthan said:
1 decade ago
I didn't get from wer did the 60/90 ratio come! can anybody?
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