1.  A man can row upstream 10 km/ph and downstream 20 km/ph. Find the man rate in still water and rate of the stream.

0,5
5,5
15,5
10,5

```Answer

Answer: Option  C Explanation:Rate in still water = 1/2(20+10) = 15 km/ph
Rate of current = 1/2(20-10) = 5 km/ph  ```

Report

2.  A man takes 3 hours 45 minutes to row a boat 15 km downstream of a river and 2 hours 30 minutes to cover a distance of 5 km upstream.Find the speed of the river current in km/hr?

0.5 km/hr
1 km/hr
2 km/hr
2.5 km/hr

```Answer

Answer: Option  B Explanation:Rate downstream = (15/3 3/4)km/hr = (15*4/15) = 4 km/hr
Rate upstream = (5/2 1/2) km/hr = (5*2/5) km/hr = 2km/hr
Speed of current = 1/2 ( 4-2) km/hr = 1 km/hr ```

Report

3.  Two persons A and B start from the opposite ends of a 450 km straight truck and run to and from between the two ends. The speed of the first person is 25 m/s and the speed of other is 35 m/s. They continue their motion for 10 hours. How many times did they pass each other?

1
4
3
2

```Answer

Answer: Option  D Explanation:First person speed = 25m/s *18/5 = 90 kmph.
Second person speed = 35m/s *18/5 = 126 kmph.
First person covers  90*10 = 900 km
900/450 = 2 ```

Report

4.  At his usual rowing rate, A can travel 12 miles downstream in a certain river in 6 hours less than it takes him to travel the same distance upstream. But if he could double his usual rowing rate for his 24 -mile round trip, the downstream 12 miles would then take only one hour less than the upstream 12 miles. what is the speed of the current in miles per hour?

1 1/3
1 2/3
2 1/3
2 2/3

```Answer

Answer: Option  D Explanation:Let the speed still in water be x mph and the speed of the current be y mph.
Speed upstream = (x-y): Speed downstream = (x+y)
12/(x-y) -12/(x+y) = 6 <=>  6(x^2 - y^2 = 24y ,<=> x^2-y^2 = 4y <=> x^2 = (4y+y^2)........(1)
And 12/(2x-y) - 12/ (2x+y) = 1 <=> 4x^2 - y^2 = 24y <=> x^2 = 24y+y^2/4 .........(2) ```

Report

5.  A man rows to a place 48 km distant and back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is?

1 km/hr
1.5 km/hr
1.8 km/hr
3.5 km/hr

```Answer

Answer: Option  A Explanation:Suppose he moves 4 km downstream in x hours. then,
speed downstream = (4/x) km/hr,  speed upstream =(3/x) km/hr.
Therefore 48/(4/x) + 48/(3/x) =14
so speed downstream = 8 km/hr, speed upstream = 6 km/hr.
Rate of the stream = 1/2 (8-6) km/hr = 1 km/hr. ```

Report