The temperature of a certain cup of coffee 10 minutes after it was poured was 120 degrees Fahrenheit. If the temperature F of the coffee t minutes after it was poured can be determined by the formula F=120(2^-at) + 60, where F is in degrees Fahrenheit and a is a constant. Then the temperature of the coffee 60 minutes after it was poured was how many degrees Fahrenheit?  Select.
A) 125
B) 95
C) 80
D) 61.8
E) 50
Answer: B   The temperature of coffee 10 minutes after it was poured (120 F) will help in solving the constant “a”.   120 = 120(2 ^ 10a) + 60   2 ^ -1 = 2 ^ 10a   a = -1/10   The temperature of coffee 60 minutes after it was poured is:   F = 120 ( 2 ^ -60/10) + 60   F = 120 * 1/ 64 + 60   F = 15/8 + 60   F = 495/8=61.8   61.8
<result>D</result>
The temperature of a certain cup of coffee 10 minutes after it was poured was 120 degrees Fahrenheit. If the temperature F of the coffee t minutes after it was poured can be determined by the formula F=120(2^-at) + 60, where F is in degrees Fahrenheit and a is a constant. Then the temperature of the coffee 60 minutes after it was poured was how many degrees Fahrenheit?