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 80 minutes after it was poured was how many degrees Fahrenheit?
Options.
A) 45	B) 56	C) 60.4	D) 85	E) 90
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 80 minutes after it was poured is:   F = 120 ( 2 ^ -80/10) + 60   F = 120 * 1/ 256 + 60   F = 15/32 + 60   F = 1935/32=60.4   60.4
<result>C</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 80 minutes after it was poured was how many degrees Fahrenheit?