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.
Rohit said:
10 years ago
Can anyone please explain me that how did you get 36/(10-x)-36/(10+x)?
Arun said:
10 years ago
How this equation came 36/(10-x)-36/(10+x) = 90/60?
Madhavan said:
10 years ago
Is there any other method to solve this?
Akshay said:
10 years ago
Miles should have been converted into meter.
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).
Ram said:
1 decade ago
Hello am not following how to take '+' n '-'in b/w: 36/(10-x) '-' 36/(10+x) = 90/60.
Suchita said:
1 decade ago
I don't understand this, please help.
Meghana said:
1 decade ago
50 can't be the answer. Because when you solve x+50=0, Then x becomes negative. Speed cannot be negative.
Rishabh said:
1 decade ago
How does it become (36)/(10-x)-(36)/(10+x)?
Ravi Kumar said:
1 decade ago
After getting X+50 and X-2 as factors of the quadratic equation, why two has been considered as answer and why not 50?
Considering X=2 is not clear. Please explain.
Considering X=2 is not clear. Please explain.
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