SOLUTION: if a boat moves by 10 km/h .and if it moves in three hours a 15 km in upstream and downstream . find the current speed of a boat. by using quadratic formula.

Question 914299: if a boat moves by 10 km/h .and if it moves in three hours a 15 km in upstream and downstream . find the current speed of a boat. by using quadratic formula.

Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
I presume it is 7.5 km each way and total time is 3 hours
let current speed = x
7.5/(10+x) +7.5/(10-x) = 3
(7.5(10-x)+7.5(10+x))/((10+x)(10-x)) = 3

(7.5(10-x)+7.5(10+x))=((10+x)(10-x))* 3

75-7.5x+75+7.5x= 3(100-x^2)
150= 300-3x^2
3x^2=150
x^2= 150/3
x^2=50
x=5sqrt(2) km/h

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