Question

The resistance, R, of a wire varies directly as its length

and inversely as the square of its diameter. If the
resistance of a wire 300 ft long with a diameter of
0.09 inches is 17113 ohms what is the resitance of
900 ft of the ame type of wire with a dister of
0.39 inches
Round off your final answer to the nearest hundredth.

Answer 1

`\qquad \qquad \textit{combined proportional variation} \\\\ \begin{array}{llll} \textit{\underline{y} varies directly with \underline{x}}\\ \textit{and inversely with }\underline{z^5} \end{array} ~\hspace{6em} \stackrel{\textit{constant of variation}}{y=\cfrac{\stackrel{\downarrow }{k}x}{z^5}~\hfill } \\\\[-0.35em] \rule{34em}{0.25pt}`

`\begin{array}{llll} \textit{\tiny`

`\textit{when L = 900 ft and d = 0.39 in, what is`

Answer 2

2733.73

Explanation:

`r = \frac{kl}{ {d}^(2) }`

`17113 = \frac{300k}{ {0.09}^(2) }`

`k = 0.462`

`r = \frac{0.462 * 900}{ {0.39}^(2) }`

`r = 2733.73`