A boat can go 20km downstream and 30 km upstream in 2hours 20minutes.Also it can go 10km downstream and 8km upstream in 49minutes.What is the speed of boat downstream in km/h?

Let, speed downstream =x =speed of boat +speed of stream speed upstream =y=speed of boat -speed of stream Now form 2 equations in x and y by equating Distance/Speed =Time Solve for x and y

let speed of boat be 'b' speed of stream be's' speed upstream = b-s speed downstream= b+s now form 2 eqns using (b+s) and (b-s) and solve them s= 2 kmph and b= 22 kmph therefore, speed downstream= b+s = 24 kmph