Question

a Boat goes 24 km upstream and 28 km downstream in 6 hours it goes 30 km upstream and 21 km downstream in 6 and half hours find the speed of the boat in still water

Answer 1

if speed of the boat be x and stream speed be y 

from the given question, 

24/(x-y) + 28/(x+y) = 6 
30/(x-y) + 21/(x+y) = 6.5 

Taking 1/(x-y) as X and 1/(x+y) as Y 
24X + 28Y = 6 
30X + 21Y = 6.5 

solving for X and Y==> 
X = 1/6 and Y = 1/14 

so x-y = 6 and x+y = 14 
hence 
x = 10 kmph and y = 4kmph