Posted by CRYSTAL on Monday, October 24, 2011 at 10:07am.
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 19 knots. How fast (in knots) is the distance between the ships changing at 5 PM? (Note: 1 knot is a speed of 1 nautical mile per hour.)

CALCULUS  Steve, Monday, October 24, 2011 at 11:40am
After t hours, distance d is
d^2 = (40+23t)^2 + (19t)^2
2d dd/dt = 2(40+23t)(23) + 2(19t)(19)
When t=5, d^2 = 155^2 + 95^2, d=181.8
2(181.8) dd/dt = 2(155)(23) + 2(95)(19)
363.6 dd/dt = 10740
dd/dt = 29.5 knots
check my math . . . 
CALCULUS  John Lee, Thursday, March 8, 2012 at 4:36pm
Your math be wrong.