At noon, ship A is 125 km east of ship B.
Ship A is sailing west at 35 km/hr, and ship B is sailing north at 35 km/hr.
How fast is the distance between the ships changing at 2:00 P.M.?
I hope you made a sketch . . .
35t | \ x
* - - - - - - - * - - - - - - *
Q 125-35t A 35t P
: - - - - - - 125 - - - - - - :
At noon, ship A is at point P.
In hours, it has moved 35t km to point A.
Then: , and
At noon, ship B is at point Q.
In hours, it has moved 35t km to point B.
Their distance is: .
So we have: .
Can you finish the problem?