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

Answer is 9

Because
difference between 10°c above zero and 8°c below zero is 10-(-8)=18°
and 18/2 =9
so we should add 9 hrs for 12
that implies 21 that means 9 is the answer we need

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Answer 2

Solution : Temperature at 12 Noon = 10°C above 0°C = 10°C

              It decreases at 2° per hour.

Final temperature = 8°C below 0 = -8°C

Change in temperature = 10 - ( -8 ) = 18°C.

Rate of decrease = 2° per hour.

Time = 18 / 2 = 9 hours.

So, Time at which temperature would be 8°C below zero = 12:00 + 9:00 = 21:00

                  So, the time at which temperature goes 8°C below 0 is 9:00 PM.

Also, The temperature at 12 :00 PM = 10° C, As temperature decreases at 2°C,

Temperature at mid night = 10° C - 2 ( 12 ) = 10 - 24 = -14° C.