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January 29, 2015

January 29, 2015

Posted by **sara** on Tuesday, October 16, 2012 at 2:53am.

- calculus -
**Reiny**, Tuesday, October 16, 2012 at 9:18amsame question ....

http://www.jiskha.com/display.cgi?id=1333489636

just change the necessary numbers

- calculus -
**Steve**, Tuesday, October 16, 2012 at 11:04amsince you have a calculus class, you probably ought to do it Reiny's way, but sometimes a little simplification can save you some work:

If the man is x away from pole, ad his shadow length is s, then using similar triangles,

s/2 = (x+s)/6

s = 1/2 x

so, ds/dt = 1/2 dx/dt

since the tip of the shadow is x+s from the pole, it is moving at

dx/dt + ds/dt = dx/dt + 1/2 dx/dt = 3/2 dx/dt = 3/2(1.4) = 2.1 m/s

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