Relationship Between Resistivity and Conductor Dimensions

[calculator20]

Homework Statement

A cylindrical conductor of length l, diameter D and resistivity ρ has resistance R. A different
cylindrical conductor of resistivity 2ρ, length 2l and diameter 2D has a resistance

A. 2R.
B. R.
C. R/2.
D. R/4

Homework Equations

I assume its R = pL/A

The Attempt at a Solution

I tried putting 2p2L/2A into the equation getting 4/2 = 2 then dividing both sides by 2 to give R/2 but apparently the answer should be B. R? Not sure how?

 

[gneill]

The cross sectional area is proportional to the square of the diameter.