Question

In a stream running at 2 km/h, a motor boat goes 10 km upstream and back again to the starting point in 55 min. Find the speed of the motorboat in still water.​

Answer 1

Answer:

22 km/hr

Step-by-step explanation:

let the speed of motor boat in still water be X km/hr

speed downstream =(x+2)km/hr

speed upstream=(x-2) km/hr

therefore (10/x-2) + (10/x+2)

=55/60

11x^2-240x-44=0

x=22

rate in still water=22 km/hr

Answer 2

let the speed of motor or boat in still waters be X kmph

Speed downstream =(X+2)kmph

speed up streams=(x-2)kmph

therefore

10/x-2+10/X+2=55/60

1/x-2+1/X+2=55/600=11/120

11xsquare-240square-40=0

(x-2)(11x+2)=0

X=22

therefore, speed of motor boat in still waters =22kmph