Question

A boat can be rowed 9 km. upstream or
18 km. downstream in a period of 3 hrs. What is the
speed of the boat in still water in km/hr?

Answer 1

Step-by-step explanation:

Given  

A boat can be rowed 9 km. upstream or 18 km. downstream in a period of 3 hrs. What is the speed of the boat in still water in km/hr?  

• Let the speed of boat in still water be a km / hr and speed of stream be b km / hr.
• Speed of boat in upstream = (a – b) km / hr
• Speed of boat in downstream = (x + y) km/hr
• Now we get 9 / a – b = 3
• Or a – b = 3-------------1
• 18 / a + b = 3
• Or a + b = 6--------------2
• Adding 1 and 2 we get
• 2 a = 9
• Or a = 9/2 = 4.5 km/hr