A boat goes up a river 20 km and down the river 24 km in 8 hours. it also goes up a river 30 km and down the river 28 km in 11 hours.What is the speed of the boat and the river?

• Speed of the boat=6 km/hr, river=2 km/hr
  
  If Boat speed=x, river/stream speed=y, Upstream Speed=x-y & Downstream speed=x+y
  1st Condition: 20/(x-y) + 24/(x+y) =8 ---(i) and
  2nd Condition:30/(x-y) + 28/(x+y) =11 ---(ii)
  For simplification, take x-y=a & x+y=b, then (i) & (ii) becomes
  (20/a)+(24/b)=8 ---(iii) &
  (30/a)+(28/b)=11 ---(iv)
  From (iii) & (iv), b=2a
  Substituting this value in (iii) or (iv), we get a=4, b=8
  So, x-y=4 & x+y=8, hence x=6, y=2
  
• 9 years agoHelpfull: Yes(12) No(2)