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 1 of 3.
Kas said:
1 decade ago
How to calculate the required time ?
Something said:
1 decade ago
Please tell me how to calculate ?
Vikas said:
1 decade ago
In this, why we calculate average?
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
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.
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.
Abhisek said:
1 decade ago
How is downstream 6km/hr?
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.
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.
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?
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