A man 6 ft tall walks at the rate of 5 ft/sec toward a streetlight that is 16 ft tall. At what rate is the length of the shadow changing when he is 10 ft from the base of the light?

Question

anonymous · Answer

I have a picture drawn out but I don't understand how to set up an equation and take its derivative.

ddcamp · Answer

|dw:1369691752162:dw|

anonymous · Answer

Oh I wasnt using two variables!

anonymous · Answer

But after I get this what do I do?

anonymous · Answer

I think I have the right answer,
y'(t)= 6/10 *dx/dt
y'(t) = 6/10 * 5
y'(t) = 3 ft/sec

radar · Answer

An excellent drawing which clearly shows the necessary relationships to solve.