Two boats start from opposite banks of river perpendicular to the shore. One is faster then the other. They meet at 720 yards from one of the ends. After reaching opposite ends they rest for 10mins each. After that they start back. This time on the return journey they meet at 400yards from the other end of the river. Calculate the width of the river.

• Let us assume that width of river d yards and speed of boats - x and y yards/min respectively.Hence the two equations are :1) (d-720)/x = 720/y2) (d/y+10+400/y) = (d/x + 10 + (d-400)/x)Solving the two equationsWe get d=1760 yard
• 13 years agoHelpfull: Yes(5) No(2)
• Let width of the river is D and distance covered by Boat A and B are a and b respectively.
  
  Sum of distance covered by A and B will be width of the river for the first meet.
  
  D = a + b ----------------------------------------- (1)
  
  Given, when they pass each other they are 720 yards from one shoreline, it means one of the boat has covered 720 yards.Say that boat is A.
  
  a = 720 yards ------------------------------------------------------ (2)
  
  By the second passing, each boat has covered the width of the river, and turned around. Then together, the boats have covered the width of the river once more, so the sum of the distances they've traveled is three times with width of the river. Since they travel at a constant rate, and together they've gone three times as far as when they first passed, it follows that one of them has traveled a distance of 3a and the other has traveled 3b.
  
  When the boats passed a second time, 400 yards from the "other" shoreline, it follows that the same boat that had traveled 720 yards by their first passing has traveled D+4000 yards by the second passing.
  
  3a = D + 400 ------------------------------------ (3)
  
  Now, Putting the value of equation (2) in equation (1).
  
  3*720 = D + 400
  
  D = 1760 yards.
• 6 years agoHelpfull: Yes(3) No(0)
• @srujan how to solve 3 unknowns with two equations
• 10 years agoHelpfull: Yes(1) No(0)