Some Problems on Boats and Streams 2

6)The speed of the boat in still water is 10km/hr and the rate of the current is 3 km/hr. The distance travelled downstream in 12 minutes is ?

solution : Speed downstream =(10+3)kmph= 13kmph

Distance travelled = 13*12/60 = 2.4 kmph

7)what is the speed of the boat in still water ?

i)The speed downstream of the boat is twice the speed upstream.

ii)The sum of the speeds of the boat , upstream and downstream is 12kmph

solution: Let the speed of the boat be x km/hr . Then

i) Speed downstream = 2x km/hr

ii)Says, the speed of the boat in still water = (1/2*12) = 6km /hr

8)A man can row upstream at 5kmph and downstream at 15kmph .The speed of the stream is ?

Solution : Speed of the stream = 1/2 (15-5) = 5kmph

9)A boat takes a total time three hours to travel downstreams from P to Q and the upstream back from Q to P. what is the speed of boat in still water ?

i)The speed of the river current is 1 km per hour

ii)The distance between P and Q is 4 km.

solution : i) The speed of the current = 1km/hr

ii)PO =4km

let the speed of the boat in still water be x km/hr

4/(x+1) +4/(x-1) =3

10)A man takes twice long to row a distance against the stream as to row the same distance in favour of the stream .the ratio of the speed of the boat in still water is ?

solution : Let man’s upstream be xkmph . then . his rate downstream =3x km/hr

(Speed in still water) : (Speed of stream ) = (2x+x/2) : (2x-x/2) =3x/2 : x/2

=> 3:1