disappears in 50 years, how much will remain after 100 years ? Ans. 90.25Y% 2. Ifa thermometer is taken outdoors where the temperature is 0°C from a room in which the temperature is 21°C and the reading drops to 10°C is I minute, how long after its removal will the reading be 5°C? Ans. 2 minutes, 13 seconds.