In a thermometer calibration test 0.31 OHM are registered when the temperature is 422 (K),
according to R=R0*e^(A*((1/T)-(1/T0))) where A is a constant, R0 is in OHMs, and T0 in (K).
If a R0=2.2 OHM for T0=310 (K), calculate R for 390 (°F).

Question

In a thermometer calibration test 0.31 OHM are registered when the temperature is 422 (K),
according to R=R0*e^(A*((1/T)-(1/T0)))  where A is a constant, R0 is in OHMs, and T0 in (K).
If a R0=2.2 OHM for T0=310 (K), calculate R for 390 (°F).

anonymous · Answer

First, you need to find the value of A. Use the initial conditions along with the measured readings to find A. 
R=Ro*e^A*(1/T-1/To)
so A = [ln(R/Ro)]/(1/T-1/To) = [ln(.31/2.2)]/(1/422-1/310)
to find R for 390 F, convert F to Kelvin... 390 F = 472 K
then used this value of T along with the value of A you calculated.
so
R=Ro*e^A*(1/T-1/To)
  =2.2*e^2289*(1/472-1/310)

anonymous · Answer

thank you very much, I thought the first condition was R=R0*e^A*(1/T-1/422), the second R=0.22*e^A*(1/T-1/310) and the last R=Ro*e^A*(1/T-1/472), because only T0 is the registered temperature, I'll ask about both ideas, maybe the problem was not worded nicely