A boat travels 43 miles upstream and 29 miles downstream in 5 hour and 12 minutes.

Question

If the speed of the boat in still water is 17 mph, find the speed of the current.  

Answer 1

Let's say the speed of current = x mph

Speed of boat = 17 mph

 

When, boat is traveling upstream, the water current is opposite to the direction of boat, thereby slowing the speed down to (17-x) mph

When, boat is traveling downstream, the water current flows in the direction of the boat, thereby increasing the speed to (17+x) mph

 

Now, we'll apply the time = distance/speed formula

The time boat takes in traveling 43 miles upstream = 43/(17-x)

And, the time boat takes in traveling 29 miles downstream = 29/(17+x)
Total time is given as 5 hours 12 min = 5.2 hours (since 60 min = 1 hour => 12 min = 0.2 hours)

Therefore, 43/(17-x) + 29/(17+x) = 5.2

This equation will result in a quadratic, which can be easily solved to give:

x = 6.1 mph