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December 22, 2014

December 22, 2014

Posted by **agora** on Thursday, May 2, 2013 at 5:41am.

(a) at what rate are they approaching or separating at the end of one hour?

(b) At what rate are they approaching or separating at the end of two hours?

(c) When do they cease to approach each other and how far apart are they at that instant

- calculus -
**Steve**, Thursday, May 2, 2013 at 11:37amLet B start at (0,0). Then the positions of the boats at time t are

A(t) = (0,50-25t)

B(t) = (20t,0)

and the distance d is thus

d^2 = (20t)^2 + (50-25t)^2

= 1025t^2 - 2500t + 2500

2d dd/dt = 2050t - 2500

At t=1, d ~= 32

64 dd/dt = 2050-2500

dd/dt = -7.03 km/hr

At t=2, d = 40

80 dd/dt = 4100-2500

dd/dt = +20

dd/dt=0 when t=1.22 so d = 31.23

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