## 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