Question

The temperature at 12 noon was 10°C above zero. If it decreases at the rate of 2°C per hour until midnight, at what time would the temperature be 8°C below zero? What would be the temperature at midnight?

Answer 1

Initial temperature i.e., at 12 noon = 10°C

Change in temperature per hour = −2°C

Temperature at 1:00 PM = 10°C + (−2°C) = 8°C

Temperature at 2:00 PM = 8°C + (−2°C) = 6°C

Temperature at 3:00 PM = 6°C + (−2°C) = 4°C

Temperature at 4:00 PM = 4°C + (−2°C) = 2°C

Temperature at 5:00 PM = 2°C + (−2°C) = 0°C

Temperature at 6:00 PM = 0°C + (−2°C) = −2°C

Temperature at 7:00 PM = −2°C + (−2°C) = −4°C

Temperature at 8:00 PM = −4°C + (−2°C) = −6°C

Temperature at 9:00 PM = −6°C + (−2°C) = −8°C

Therefore, the temperature will be 8°C below zero at 9:00 PM.

Now,

Temperature at 10:00 PM = −8°C + (−2°C) = −10°C

Temperature at 11:00 PM = −10°C + (−2°C) = −12°C

Temperature at 12:00 AM = −12°C + (−2°C) = −14°C

Therefore, the temperature at midnight will be −14°C below 0.