Calc -- related rate?

Question

At noon, ship A is 40 nautical miles due west of ship B. Ship A is sailing west at 23 knots and ship B is sailing north at 16 knots.

How fast (in knots) is the distance between the ships changing at 7 PM?

(Note: 1 knot is a speed of 1 nautical mile per hour.)

Answer 1

The best way to find the answer is to draw it.  Make a line left to right (representing west and east) of a length you find easy to measure and read an increment of Nautical mile (nm).  Say 40 mm.  Then make a line due noth of ship B, 16 (nm) x 7 (hrs).  Draw a line due west for Ship A 27 x 7, mm.  Then measure the distance between the two points and divide by 7.  That will give you the opening rate of the two ships.

There may be more scientific approaches but this is the uncomplicated old fashioned way.

Good Luck