Question 934114
    A RACE- BOAT COVERS A DISTANCE OF 66 KM DISTANCE DOWNSTREAM IN 110 MINUTES. IF COVERS THIS DISTANCE UPSTREAM IN 120 MINUTES. THE SPEED OF THE BOAT IN STILL WATER IS 3.45 KM/HR. FIND THE SPEED OF THE STREAM.
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let x=speed of stream
(3.45+x)=speed of boat downstream
(3.45-x)=speed of boat upstream 
distance/speed=travel time
..
{{{66/((3.45+x))=110/60}}}
{{{66/((3.45-x))=120/60}}}
..
{{{66/((3.45+x))=11/6}}}
{{{66/((3.45-x))=2}}}
..
{{{66/((3.45+x))=11/6}}}
{{{66/((3.45-x))=2}}}
..
6(66)=11(3.45+x)
66=2(3.45-x)
..
396=37.95+11x
66=6.90-2x
..
792=75.9+22x(mult. eq by2)
726=75.9-22x(mult. eq by11)
subtract
44x=66
4x=6
x=6/4=1.5
speed of stream=1.5 km/hr