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 9 of 9.
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.
Hussain peera said:
1 decade ago
Can we find solution to this problem in different manner it means any shortcut.
Honey said:
1 decade ago
x2+48x-100 = 0.
x2+50x+2x-100 = 0.
x(x+50)-2(x+50) = 0.
(x+50)(x-2) = 0.
x = 2.
x2+50x+2x-100 = 0.
x(x+50)-2(x+50) = 0.
(x+50)(x-2) = 0.
x = 2.
Bala said:
1 decade ago
Answer: Option A.
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.
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.
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