Temperature at 12pm = 10°C
Temperature decreases at 2°C per hour
we need to find, time when temperature is 8°C below zero, ie., -8°C
∴ Total decrease = Final temperature – initial temperature = -8°C -10°C
= -8 – 10 = -18°C
Now,
Temperature decrease in 1 hour × Total number of hours = Total decrease
So, temperature becomes -8°C = 9 hours
∴ Temperature is -8°C at 9PM
Now,
We need to find temperature at mid – night temperature at 12AM = Temperature at 12PM
Temperature change in 12 hours
Temperature change in 1 hour = -2°C
Temperature change in 12 hour = -2 × 12°C = -24°C
Now,
Temperature at 12AM – Temperature at 12PM = Temperature change in 12 hours. Temperature at 12AM – 10°C = -24°C
Temperature at 12AM = – 24°C + 10°C
Temperature at 12 AM = -14°C
∴ Temperature at Mid – night = -14°C