Question

The temperature at 12 noon was 12℃ above zero (0). If it decreases at the rate of 2℃ per hour until midnight.
(i) What time would the temperature be below 0℃
(ii) What would be the temperature at midnight?

Answer 1

Temperature at 12 noon = 12℃
Temperature is decreasing at the rate of 2℃ per hour
(i) After 1 hour, temperature will be = 12 - 2 = 10℃
After 2 hours, temperature will be = 10 – 2 = 8℃
After 3 hours, temperature will be = 8 – 2 = 6℃
After 4 hours, temperature will be = 6 – 2 = 4℃
After 5 hours, temperature will be = 4 – 2 = 2℃
After 6 hours, temperature will be = 2 – 2 = 0℃
After 7 hours, temperature will be = 0 – 2 = -2℃
Therefore, After 6 hour’s temperature will be below 0℃.
12 PM + 6 hours after that = 6 PM
Hence the temperature will be below 0℃ after at 7 PM

(ii) After 8 hours, temperature will be = – 2 – 2 = -4℃
After 9 hours, temperature will be = - 4 – 2 = -6℃
After 10 hours, temperature will be = - 6 – 2 = -8℃
After 11 hours, temperature will be = - 8 – 2 = -10℃
After 12 hours, temperature will be = - 10 – 2 = -12℃
Therefore the temperature at midnight will be -12℃.