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.
Prachiti said:
9 years ago
How to solve this question if the rate for going downstream is not given?
Ashoka said:
9 years ago
From the last second step 25/18 * 18/5 from where 18/5 came?
Rajesh said:
8 years ago
How 15/2 came? Explain.
Parag said:
8 years ago
How did 450 came?
Bhavuk said:
8 years ago
From where 450 has come?
Sriteja said:
8 years ago
Anyone, please explain conversion from meters to kilometers in this problem.
Tejaswini said:
8 years ago
How did 450? please explain it.
Chan said:
7 years ago
1000 Meters = 1 KM.
3600 seconds = 1 Hour.
So to convert meters into KM you need to divide that number by 1000 and similarly to convert seconds into Hour you need to divide that number by 3600.
3/4th of a KM = 750 meters,
11 1/4 minutes = 45/4 minutes = convert to seconds = 45/4 * 60 = 675 seconds.
Now, convert meters/seconds into km/hrs like the below;
750/1000
------------
675/3600
which is equal to;
750/675 * 3600/1000 = 4 km/hr = Speed of upstream.
Similarly, calculate for downstream and then take an average of the sum to get the answer.
3600 seconds = 1 Hour.
So to convert meters into KM you need to divide that number by 1000 and similarly to convert seconds into Hour you need to divide that number by 3600.
3/4th of a KM = 750 meters,
11 1/4 minutes = 45/4 minutes = convert to seconds = 45/4 * 60 = 675 seconds.
Now, convert meters/seconds into km/hrs like the below;
750/1000
------------
675/3600
which is equal to;
750/675 * 3600/1000 = 4 km/hr = Speed of upstream.
Similarly, calculate for downstream and then take an average of the sum to get the answer.
Chan said:
7 years ago
1000 Meters = 1 KM.
3600 seconds = 1 Hour.
So to convert meters into KM you need to divide that number by 1000 and similarly to convert seconds into Hour you need to divide that number by 3600.
3/4th of a KM = 750 meters,
11 1/4 minutes = 45/4 minutes = convert to seconds = 45/4 * 60 = 675 seconds.
Now, convert meters/seconds into km/hrs like the below;
750/1000
------------
675/3600
which is equal to;
750/675 * 3600/1000 = 4 km/hr = Speed of upstream.
Similarly, calculate for downstream and then take an average of the sum to get the answer.
3600 seconds = 1 Hour.
So to convert meters into KM you need to divide that number by 1000 and similarly to convert seconds into Hour you need to divide that number by 3600.
3/4th of a KM = 750 meters,
11 1/4 minutes = 45/4 minutes = convert to seconds = 45/4 * 60 = 675 seconds.
Now, convert meters/seconds into km/hrs like the below;
750/1000
------------
675/3600
which is equal to;
750/675 * 3600/1000 = 4 km/hr = Speed of upstream.
Similarly, calculate for downstream and then take an average of the sum to get the answer.
Cidhu said:
7 years ago
thank u @Sanchit
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