Question

the speed at which a man rows downstream is 3 km/h more than that at which he rows upstream. he rows 1 km upstream and comes back to his starting point in half an hour. What is the speed at which he rows downstream

Answer 1

Answer:

6 km/h

Step-by-step explanation:

Speed downstream = (x+3) km/h (let)

Speed upstream = x km/h

While going upstream,

Distance = 1 km

time = 1/x h

While going downstream,

Distance = 1 km

time = 1/(x+3) h

A.T.P.

1/x + 1/(x+3) = 1/2

2*(x+3+x)  = x(x+3)

4x + 6 = x^2 + 3x

x^2 -x -6 = 0

x^2 -3x +2x -6 = 0

(x+2)(x-3)=0

x=3 (since time cannot be negative)