1.  A man can row upstream at 7 km/ph and downstream at 10 km/ph.Find man's rate in still water and the rate of current?

1.5 km/hr
2.5 km/hr
3 km/hr
2 km/hr

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Answer: Option  A Explanation:Rate in still water = 1/2 (10+7) km/hr =8.5 km/hr
Rate of current = 1/2 (10-7) km/hr = 1.5 km/hr ```

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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

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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 ```

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3.  A man can row at 18 km/ph in still water.It takes him thrice as long to row up as to row down the river.Find the rate of stream.

6 km/hr
7 km/hr
9 km/hr
8 km/hr

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Answer: Option  C Explanation:Let man's rate upstream be X km/ph.Then his rate downstream = 3x km/ph
Rate in still water = 1/2 (3x+x) km/ph =2x
2x = 18 so X= 9
Rate upstream = 9 km/hr; Rate downstream = 27 km/hr
Hence rate of stream = 1/2 ( 27-9) km/hr = 9 km/hr ```

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4.  There is a road beside a river.Two friends started from a place A moved to a temple situated at another place B and then returned to A again.One of them moves on a cycle at a speed of 12 km/hr while the other sails on a boat at a speed of 10 km/hr.If the river flows at the speed of 4 km/hr which of the two friends will return to place A first?

7 km/hr
8 km/hr
8.4 km/hr
9.2 km/hr

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Answer: Option  C Explanation:Clearly the cyclist moves both ways at a speed of 12 km/hr
so average speed of the cyclist = 12 km/hr
The boat sailor moves downstream at ( 10+4) i.e, 14 km/hr and upstream at (10-4) i.e, 6 km/hr
So average speed of the boat sailor =(2*14*6/14+6) km/hr = 42/5 km/hr = 8.4 km/hr
since the average speed of the cyclist is greater he will return to A first. ```

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5.  A man can row 7 1/2 km/ph in still water.If in a river running at 1.5 km an hour it takes him 50 minutes to row to place and back how far off is the place?

4 km
5 km
6 km
3 km

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Answer: Option  D Explanation:Speed downstream = (7.5+1.5) km/ph = 9 km/ph
Speed upstream = (7.5 - 1.5) km/hr = 6 km/ph
Let the required distance be X km.
x/9 +x/6 = 50/ 60 = 2x+3x =( 5/6*18) = 5x = 15 = x= 3 km. ```

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