Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 11)
11.
A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 5 km in stationary water?
Answer: Option
Explanation:
| Rate downstream = |  |
1 | x 60 |  km/hr = 6 km/hr. |
| 10 |
Rate upstream = 2 km/hr.
| Speed in still water = | 1 | (6 + 2) km/hr = 4 km/hr. |
| 2 |
 Required time = |
|
5 | hrs = 1 |
1 | hrs = 1 hr 15 min. |
| 4 | 4 |
Discussion:
27 comments Page 2 of 3.
Kiran said:
8 years ago
The ans must be 1hr 25mins.
5/4=1.25.
How it can be 1hr 15mins?
5/4=1.25.
How it can be 1hr 15mins?
(2)
Rajesh Rapelly said:
9 years ago
Let Speed of the boat is 'u' and Speed of the Stream is 'v'.
Then u+v=6km/hr ///Speed of the boat in downstream.
Then u-v=2km/hr ////Speed of the boat in upstream.
Here we need the speed of the boat in Still Water which is 'u', because the speed of stream is zero in still water i.e;v=0.
By solving u+v =6 & u-v=2 ,we get u=4km/hr.
Ao, Speed of the boat in Stillwater is 4km/hr, then to travel 5km it take 1hr 15mins.
Then u+v=6km/hr ///Speed of the boat in downstream.
Then u-v=2km/hr ////Speed of the boat in upstream.
Here we need the speed of the boat in Still Water which is 'u', because the speed of stream is zero in still water i.e;v=0.
By solving u+v =6 & u-v=2 ,we get u=4km/hr.
Ao, Speed of the boat in Stillwater is 4km/hr, then to travel 5km it take 1hr 15mins.
Rohini said:
9 years ago
The question says a boatman goes 2 km against the current of the stream in 1 hour which means upstream so, it is 2km/hr.
(1)
Darth vadar said:
9 years ago
Divide 5 by 4 we get 0.25. So why the answer is 1 hr 15 min instead of 1 hr 25 min.
Anu said:
10 years ago
How can rate upstream be 2 km/hr?
Sowmya said:
10 years ago
I can't understand, please help me.
Lohith said:
10 years ago
s = d/t;
u-v = 2/1;
u-v = 2.
u+v = 2/10/60.
u+v = 12.
u = 7.
v = 5.
Final value = 5/7 which is less than a hour.
u-v = 2/1;
u-v = 2.
u+v = 2/10/60.
u+v = 12.
u = 7.
v = 5.
Final value = 5/7 which is less than a hour.
Suchita said:
10 years ago
I am still confuse for conversion of time. Please somebody can help me to understand all types of conversion of time.
Here they have divided in some problem they have multiplied it.
Here, 3/10*60 and in one example 18*12/60, why like this?
Here they have divided in some problem they have multiplied it.
Here, 3/10*60 and in one example 18*12/60, why like this?
MohitRaj said:
1 decade ago
We know that,
Upstream speed = u-v;
Downstream speed=u+v;.
According to formula, s=d/t.
u-v = 2/1, and
u+v = 60/10.
On solving these equations, we get.
u=4 and v=2.
Therefore, speed of boatman = 4 km/hr.
Hence, t=d/s.
t=5/4.
We get 1hr 15min is answer.
Upstream speed = u-v;
Downstream speed=u+v;.
According to formula, s=d/t.
u-v = 2/1, and
u+v = 60/10.
On solving these equations, we get.
u=4 and v=2.
Therefore, speed of boatman = 4 km/hr.
Hence, t=d/s.
t=5/4.
We get 1hr 15min is answer.
Anjali said:
1 decade ago
See here.
Since downstream = 1km (10mins).
So for 10 mins = 1km.
So from this when we convert to hrs we get.
10/60 =1 km.
And that 60 goes to rhs it will be multiplied with kms.
i.e., 10=1*60.
So 1 hr = 6 kms.
Since downstream = 1km (10mins).
So for 10 mins = 1km.
So from this when we convert to hrs we get.
10/60 =1 km.
And that 60 goes to rhs it will be multiplied with kms.
i.e., 10=1*60.
So 1 hr = 6 kms.
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