Aptitude - Boats and Streams - Discussion

Discussion Forum : Boats and Streams - General Questions (Q.No. 7)
7.
The speed of a boat in still water in 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is:
1.2 km
1.8 km
2.4 km
3.6 km
Answer: Option
Explanation:

Speed downstream = (15 + 3) kmph = 18 kmph.

Distance travelled = 18 x 12 km = 3.6 km.
60

Video Explanation: https://youtu.be/IDOwWUeOldQ

Discussion:
21 comments Page 2 of 3.

Kanchan Tarwani said:   2 decades ago
why we add current rate with speed of still water??

Gautam said:   1 decade ago
Use the formula= if the speed of a boat in still water is U km/hr and the speed of the stream is V km/hr, then

speed down stream = (u+v)km/hr
(15+3)km/hr = 18 km/hr

Distance travelled = (18 x 12/60)=3.6km ANSWER
[60 is here because 1 minute=60seconds]

Angu said:   1 decade ago
Thanks bindu

Satish said:   9 years ago
Speed of boat in still water and speed of boat are different.

Why all are using this same u + v for still water? It's not correct. Both are different.

Sairam said:   9 years ago
@Lalitha.

Because time is in minutes, we have to change its unit of time from minutes to hours. So we have divide it.

If the distance is in meters then we have to multiply, to change it to seconds.

Vinayak Mahadev said:   8 years ago
Speed of down stream= Still water speed + rate of current speed.

= 15 + 3 = 18.

18km/hrs for 1 hour (60 min).
Then find 12 min.
18 : 60
x : 12.
x= (12*18)/60 =3.6min.
That's all.

Bindu said:   1 decade ago
Rate of current=1/2(downstream speed- upstream speed)
ie=1/2[(U+V)-(U-V)]
=1/2(U+V-U+V)
=2V/2
=V
SO RATE OF CURRENT = V(SPEED OF STREAM)

Ananda said:   6 years ago
If we calculate the same question in upstream. Then the solution is;

Sanjana said:   1 decade ago
Why we add current rate with speed?

Nagarjun said:   1 decade ago
They have specified as downstream so we have to add.


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