Posted by Sandra g on Thursday, March 15, 2012 at 9:30pm.
at noon A is 150 km west of a ship B .Ship A is sailling east at 35 km/h , and ship B is sailling north at 25 km/h. How fast is the distance between the ships changing at 4 pm ?

Calculus  Steve, Friday, March 16, 2012 at 11:44am
the distance between the ships at time t is
d^2 = (15035t)^2 + (25t)^2
at t=4,
d^2 = (150140)^2 + (100)^2 = 100 + 10000 = 10100, so d=100.5
2d dd/dt = 2(15035t)(35) + 2(25t)(25)
at t=4,
201 dd/dt = 700 + 5000
dd/dt = 21.39km/h