Question

The temperature at 12 noon was 10°C above zero. If it decreases at the rate of 2°C per hour
until midnight.
(i) At what time would the temperature be −8°C?
(ii) What would be the temperature at mid-night?
(iii) At what time would the temperature be 0°C?

Answer 1

Answer

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.

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