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 3 of 3.
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.
Abhisek said:
1 decade ago
How is downstream 6km/hr?
Arun.D said:
1 decade ago
Upstream=2km (1 hr).
Downstream =1km (10 min).
For 10 min=1 km.
For 1 hr = 6 km.
Speed in still water = 1 /2(a + b) km/hr.
Speed of still water = 1/2(2+6).
= 1/2(8).
= 4km/hr.
Time = distance/time.
Time taken to go 5 km in stationary water = (5/4).
= 1hr 25min.
Downstream =1km (10 min).
For 10 min=1 km.
For 1 hr = 6 km.
Speed in still water = 1 /2(a + b) km/hr.
Speed of still water = 1/2(2+6).
= 1/2(8).
= 4km/hr.
Time = distance/time.
Time taken to go 5 km in stationary water = (5/4).
= 1hr 25min.
Narendar said:
1 decade ago
We can do this question by another way.
Let us suppose speed od boat is we and speed of stream is v1.
When boat against the current then speed =v-v1.
And when boat along the current then speed =v+v1.
v-v1=2/1;.
v+v1=1/ (10/60).
Calculate the value of v.
I got value of v 4km/h.
T=5/4.
T=1 hr 15 min.
Let us suppose speed od boat is we and speed of stream is v1.
When boat against the current then speed =v-v1.
And when boat along the current then speed =v+v1.
v-v1=2/1;.
v+v1=1/ (10/60).
Calculate the value of v.
I got value of v 4km/h.
T=5/4.
T=1 hr 15 min.
Sravankumar said:
1 decade ago
We caluculate required time by using this formule
t=l/s.
Here t=5km/4hrs leads to (5/4)km per hour
t=l/s.
Here t=5km/4hrs leads to (5/4)km per hour
Vikas said:
1 decade ago
In this, why we calculate average?
Something said:
1 decade ago
Please tell me how to calculate ?
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