Answer :
Answer:
The speed of a boat in still water is 30 mph. It takes the same time for the boat to travel 5 miles upstream as it does to travel 10 miles downstream. Find the speed of the current.
Solution. The key to this type of problem is same time. That will give the equation,
Time upstream = Time downstream
Now, speed, or velocity, is distance divided by time -- so many miles per hour:
v =d
t
Therefore,
t =d
v
The equation will be
Time upstream=Time downstream Distance upstream
Speed upstream =Distance downstream
Speed downstream Let x be the speed of the current. Then according to the problem: _5_
30 − x= 10
30 + x Therefore,5(30 + x)=10(30 − x) 150 + 5x=300 − 10x 5x + 10x=300 − 150 15x=150 x=10 mph