Posted by **meen** on Thursday, November 22, 2012 at 9:42am.

A boat sails 30 miles to the east from a point P, then it changes direction and sails to the south. If this boat is sailing at a constant speed of 10 miles/hr, at what rate is its distance from the point P increasing

a) 2 hours after it leaves the point P

b) 7 hours after it leaves the point p

- calculus -
**Steve**, Thursday, November 22, 2012 at 7:33pm
at 10 mph, it is still going east at t=2

so, distance is increasing at 10 mph

at t=3, it turns south. After that, the distance d from P is

d^2 = 30^2 + (10(t-3))^2

since it has only been sailing south for (t-3) hours.

2d dd/dt = 200(t-3)

at t=7, d=50

2*50 dd/dt = 200(4)

dd/dt = 8 mph

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