Homework help- electrical resistance

[bob12345]

Homework Statement

A 2.5 cm length of tungsten filament in a
small lightbulb has a resistance of 0.041
.
Find its diameter. (The resistivity is
5.6 × 10−8
· m).
Answer in units of mm.

Homework Equations

R=P(L/2pi*rsquared)

The Attempt at a Solution

i keep getting 20856 m as my answer but it is wrng when i entr it i plugged in everything and made sure everything was to the right unit so don't know what is wrong

 

[ehild]

Take care of units. The resistance of the filament is 0.041 ohm, the resistvity is 5.6 x10-8 ohm-meter, and the length is 0.025 m. How could you get such a result for the diameter of a tiny filament? Show your calculation.

ehild