the resistivity of pure copper is 156 micro-ohm

Question

The resistivity of pure copper is 1.56 micro-ohm -cm.  An alloy of copper contains 1 atomic percent nickel has a resistivity of 2.81 micro-ohm-cm. An alloy of copper containing 3- atomic percent silver has a resistivity of 1.98 micro-ohm -cm. What is the resistivity of an alloy of copper containing 2 atomic percent nickel and 2 atomic percent silver?

Ans:

ρ_cu = 1.56

ρ_{(cu + Ni)}  = 2.81

ρ₁, raise in resistivity for one atomic percent-added impurity as Nickel

ρ₁( Nickel )  = 1.25 = 2.81 -1.56 = 1.25

ρ₁( Silver )  = (1.98 - 1.56)/3 = 0.14

ρ_alloy = 1.56  + 2 ×1.25  + 2 × 0.14 = 4.34 µ? - cm.