Question

A boat takes 35 min less to travel 28 km downstream than it takes to travel the same distance upstream. If the speed of the boat in still water is 14 km/h. What js the speed of the stream

Answer 1

Answer:

Given :

Let the speed of the stream be X km/h thenSpeed downstream =(15+x) km/hSpped upsstream =(15-x )km/h

40/(15-x) - 40/(15+x)=60/60

40(15+x)-40(15-x)=(15-x)²

600 +40x -600+40x= 225-x²

x² +80x -225=0

Solving the above quadratic equations we get :

X=( - b± √b²-4ac)/2a

here a=1

b= -80

c=225

b²-4ac= 6400-900 =5500

x=80± √5500/2

on solving for X we get, 

X=2.919 

Therefore speed of stream =2.919 km/hr