Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 12)
12.
A man can row three-quarters of a kilometre against the stream in 11
minutes and down the stream in 7
minutes. The speed (in km/hr) of the man in still water is:
minutes and down the stream in 7 minutes. The speed (in km/hr) of the man in still water is:Answer: Option
Explanation:
We can write three-quarters of a kilometre as 750 metres,
and 11 minutes as 675 seconds.
| Rate upstream = |  |
750 |  m/sec |
= | 10 | m/sec. |
| 675 | 9 |
| Rate downstream = | |
750 | m/sec |
= | 5 | m/sec. |
| 450 | 3 |
 Rate in still water = |
1 | |
10 | + | 5 | m/sec |
| 2 | 9 | 3 |
| = | 25 | m/sec |
| 18 |
| = | |
25 | x | 18 | km/hr |
| 18 | 5 |
= 5 km/hr.
Discussion:
42 comments Page 2 of 5.
Kishor said:
1 decade ago
Downstream : Upstream
...................................................
Distance(D) 3/4 x 1 km : 3/4 x 1 km
Time(T) 15/2 x 60 hr : 45/4 x60 hr
Speed(D/T) (3/4 x1)/(15/2 x60)=6 : (3/4 x1)/(45/4 x60)=4
Speed of man in still water = (6+4)/2 = 5 km/hr.
...................................................
Distance(D) 3/4 x 1 km : 3/4 x 1 km
Time(T) 15/2 x 60 hr : 45/4 x60 hr
Speed(D/T) (3/4 x1)/(15/2 x60)=6 : (3/4 x1)/(45/4 x60)=4
Speed of man in still water = (6+4)/2 = 5 km/hr.
Hari Gudapati said:
7 years ago
First, we convert minutes to hours i.e, 11 1/4 min to 45/4*60 hrs also 7 1/2 min to 15/2*60 hrs.
Apply formula speed = distance/ time (km/hr).
Rate upstream = 3/4 x 4x60 / 45 = 4 km/hr.
Rate downstream = 3/4 x 8/1 = 6 km/hr.
The speed of a man in still water = 1/2(4+6)= 5 km/hr.
Apply formula speed = distance/ time (km/hr).
Rate upstream = 3/4 x 4x60 / 45 = 4 km/hr.
Rate downstream = 3/4 x 8/1 = 6 km/hr.
The speed of a man in still water = 1/2(4+6)= 5 km/hr.
(1)
M Ganesh said:
5 years ago
3 Quarters means-3/4th km.
Time taken for upstream- 45/4 min.
Time taken for downstream-15/2 min.
We need to calculate upstream and downstream.
Upstream-3/4/45/4*60.
= 4km/hr.
Downstream=3/4/15/2*60.
=6km/hr.
Sb - sw = 4.
Sb + sw = 6.
Solving this eqn we will get;
Sb = 5km.
Time taken for upstream- 45/4 min.
Time taken for downstream-15/2 min.
We need to calculate upstream and downstream.
Upstream-3/4/45/4*60.
= 4km/hr.
Downstream=3/4/15/2*60.
=6km/hr.
Sb - sw = 4.
Sb + sw = 6.
Solving this eqn we will get;
Sb = 5km.
(11)
Deepi said:
1 decade ago
To convert mints to seconds just multiply by 60.
to convert mints to hour just divide by 60.
here 11 1/4 mint (11*4+1) 45/4
To convert 45/4*60=675
to convert mints to hour just divide by 60.
here 11 1/4 mint (11*4+1) 45/4
To convert 45/4*60=675
Laxman Pawar said:
5 years ago
When we cross multiply, we should get as 10.
15/2*3/4 = 10,
45/4*4/3 = 15,
10-15 = 5,
So, the Answer is 5.
15/2*3/4 = 10,
45/4*4/3 = 15,
10-15 = 5,
So, the Answer is 5.
(3)
Fahmi said:
1 decade ago
We can do it more easy way.
(3/4) * (4/45) *60 = 4 km.
(3/4) * (2/15) *60 = 6 km.
1/2 (4+6) km = 5 km.
(3/4) * (4/45) *60 = 4 km.
(3/4) * (2/15) *60 = 6 km.
1/2 (4+6) km = 5 km.
Ansh said:
6 years ago
@All.
Here, the speed of man is asked then why you have calculated the rate of water? Please explain me.
Here, the speed of man is asked then why you have calculated the rate of water? Please explain me.
(2)
Nizampatnam said:
1 decade ago
Yes Down Stream 7 1/2=15/2*60
=900/2
=450sec
=900/2
=450sec
Naveena said:
9 years ago
Hi, I'm a beginner for this type of problem. Can anyone explain this question for me?
Mohan said:
1 decade ago
How can we find the value for Rate Upstream and Rate downstream
reply plz /....
reply plz /....
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