Question 368912
let speed of boat in still water be x kmph
speed of current = 2 kmph
..
upstream speed = x-2 
downstream speed = x+2
..
t= d/r
time upstream + time downstream = 7 hours
distance = 2km
2/(x-2)+2/(x+2)=7
2(x+2)+2(x-2)/(x+2)(x-2)=7
2x+4+2x-4 = 7(x+2)(x-2)
4x=7(x^2-4)
4x=7x^2-28
7x^2-4x-28 =0
solve using quadratic equation
discriminant = 800
x1= (+4+sqrt(800))/14
x1= 2.3 km/h speed of boat in still water
x2 is negative so ignore
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m.ananth@hotmail.ca