Two large containers A and B of the same size are filled with different fluids. The fluids in containers A and B are maintained at 0 C and 100 C, respectively. A small metal bar, whose initial temperature is 100 C, is lowered into container A. After 1 minute the temperature of the bar is 90 C. After 2 minutes the bar is removed and instantly transferred to the other container. After 1 minute in container B the temperature of the bar rises 10 C. How long, measured from the start of the entire process, will it take the bar to reach 99.9 C?
This shows how to determine how long it will take for a container to reach a given temperature.