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

At 12 noon, the temperature = 10° C above zero The temperature is decreasing at 2° C per hour 8° C below zero = - 8° C So, total fall in temperature from 10° C to 0° C and from 0° C to - 8° C = 18° C Since the temperature falls 2° C in every one hour. Therefore, to decrease 18° C, time taken = 18/2 = 9 hours Present time is 12 noon so, the time when the temperature is - 8° C = 12 noon + 9 hours So, The time at which the temperature will be - 8° C = 9 PM At 9 PM, the temperature is - 8° C, the temperature at 12 midnight will be = (- 8° C) + (- 2° C × 3 hours) = (- 8° C) + (- 6° C) = - 14° C So, at 12 midnight the temperature will be - 14° C.