Understanding Resistivity: Solving a Wire Material Mystery

[Burntresistor]

Homework Statement

a 15ft length wire with a cross sectional area of 127 c mils has a resistivities of 8.74 ohms at 20 C. What material is wire made of. Any help would be appreciated. (pi/4*10^-6) was given by the book. Whats odd is when I enter pi/4*10^6 instead for wolfram I'm getting the right answer. I would just like to know if I'm wrong or the book is,and if I am wrong how to go about it.

Homework Equations

p=AR/L ([127(pi/4*10^-6)IN^2](8.74ohm))/15ft*1ft/12inch*.0254/1inch

The Attempt at a Solution

wolfram isn't giving me the right answer. I'm given this problem from a schaum workbook. answer is 12.3*10^-8

Homework Statement

Homework Equations

The Attempt at a Solution

 

[Zryn]

I get the same answer as the Schaum's book when I used SI units.

As per http://en.wikipedia.org/wiki/Resistivity" the units of R is Ohms, A is square metres and L is metres, thus giving the final unit of Ohm metres for p.

As per http://en.wikipedia.org/wiki/Circular_mil" 1 c mil = 5.067×10-10 square metres.

As per http://en.wikipedia.org/wiki/Foot_%28unit%29" 1 foot = 0.3048 metres.

So put it all together and tell us what you get.

 

[Burntresistor]

123.01 ^-9

The way the book had it presented is the way I wrote it down. This way was a lot easier. Thanks