Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 4)
4.
A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is:
Answer: Option
Explanation:
Let the speed of the stream be x km/hr. Then,
Speed downstream = (15 + x) km/hr,
Speed upstream = (15 - x) km/hr.
 |
30 | + | 30 | = 4 | 1 |
| (15 + x) | (15 - x) | 2 |
 |
900 | = | 9 |
| 225 - x2 | 2 |
9x2 = 225
x2 = 25
x = 5 km/hr.
Video Explanation: https://youtu.be/lMFnNB3YQOo
Discussion:
65 comments Page 7 of 7.
Owen said:
1 decade ago
What confuses me is that I expected the time gained going down to be same as that lost going up.
Finding the velocities etc easy way to solve this, but I still find the thought difficult to get around that whatever the stream gives in time going down should be lost going back But its just not true!
Finding the velocities etc easy way to solve this, but I still find the thought difficult to get around that whatever the stream gives in time going down should be lost going back But its just not true!
John said:
1 decade ago
What happen to the 900 and the 2?
Sagar said:
1 decade ago
In a stream running at 2km/h, a motor boat goes 10 km upstream and back again to the starting point in 55 minutes. Find the speed of the motorboat in still water? Please answer.
Lakki said:
1 decade ago
Any shortcut method for this sum?
Aary said:
1 decade ago
How did we get 30*30 = 900?
Are we taking 30 common or what?
Are we taking 30 common or what?
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