Question

In a 25 degree C room, hot coffee in a vacuum flask cools from 72 degree C to 54 degree in 8 hours.Find its temperature after another 8 hours.

Answer 1

Assume an exponential rate of decay.

T = To + (To - Ta)*ext(-kt)
where t is the time in hours. You could solve for k, but there is an easier way to do it.

In 8 hours, the initial 47 degrees above ambient temperature becomes 19 C. 40.4% of the in initial temperature difference remains after eight hours. In another 8 hours, that difference from ambient (Ta) will decrease to 0.404 * 19 = 7.7 degrees, or 32.7 degrees.

Answer 2

its telling me this is wrong