Going against the current, a boat takes 6 hours to make a 120-mile trip. When the boat travels with the current on the return trip, it takes 5 hours.

What is the rate of the boat in still water?

2 mph
20 mph
22 mph

Question

Going against the current, a boat takes 6 hours to make a 120-mile trip. When the boat travels with the current on the return trip, it takes 5 hours.



What is the rate of the boat in still water?

2 mph
20 mph
22 mph

anonymous · Answer

In other words what is the speed of the current? is the question

anonymous · Answer

We can setup 2 equations. 1 for with the current and 1 for against it

anonymous · Answer

let x be the speed of the boat.
Let y be the speed of the current.

The units of speed is miles/hr. This is important to know when setting up the equations. Our units must work out.

6x - 6y = 120    this is minus because the current is going in the opposite direction
5x + 5y = 120

Now you need to solve the system for y and I think you should get your answer. Do this by substitution. Solve 1 equation for x and substitute that into the other to solve for y.