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[Wes]

Here's one that I'm having trouble with:

At noon, ship A is 150 km west of ship B. Ship A is sailing east at 35km/h and ship B is sailing north at 25 km/h. How fast is the distance between the ships changing at 4:00pm ?

 

[Gene]

The Distance is
D=sqrt((150-35t)^2+(25t)^2)
If you need more, show what you have done with that.