Answer:
4.9 minutes
Step-by-step explanation:
Given; T(t) = Ce^-kt + Ts
Now;
T(t) = 190 degrees Fahrenheit
Ts = 60 degrees
To obtain C;
190 = Ce^0 + 60
190 - 60 = C
C = 130
Hence, to find k when t=11
172 = 130 e^-11k + 60
172 -60/130 = e^-k
e^-k = 0.86
ln(e^-k) = ln( 0.86)
-k = -0.15
k = 0.15
Hence at 122 degrees, t is;
T(t) = Ce^-kt + Ts
122 = 130e^-0.15t + 60
122 - 60/130 = e^-0.15t
0.477 = e^-0.15t
ln (e^-0.15t) = ln (0.477)
-0.15t = -0.74
t = 0.74/0.15
t = 4.9 minutes