Question

please answer fast 29

Answer 1

let the speed of boat in still water be x kmph
speed of stream be y kmph
so, speed of boat upstream x-y kmph
speed of boat downstream x+y kmph
$\frac{40}{x + y} = 2 \\ 2x + 2y = 40 \: \: \: \: \: \: \: \\ x + y = 20 \: \: \: \: \: \: \: eq1$
$\frac{40}{x - y} = 4 \\ 4x - 4y = 40\: \: \: \: \: \: \: \\ x - y = 10 \: \: \: \: \: eq2$
solve these equation
add both the equation
$2x = 30\\ x = 15 \: kmph$
$15 + y = 20 \\ y = 5 \: \: kmph$
so,speed of boat 15 kmph,and stream be 5 kmph