The temperature at 12 noon was 10oC above zero. If it decreases at the rate of 2oC per hour


until mid-night, at what time would the temperature be 8oC below zero? What would be the temperature at mid-night?

It is given in the question that,


Temperature at 12 noon = 10oC


Also,


Change in temperature per hour = - 2oC


Therefore,


Temperature at 1:00 PM = 10oC + (-2oC) = 8oC


Temperature at 2:00 PM = 8oC + (-2oC) = 6oC


Temperature at 3:00 PM = 6oC + (-2oC) = 4oC


Temperature at 4:00 PM = 4oC + (-2oC) = 2oC


Temperature at 5:00 PM = 2oC + (-2oC) = 0oC


Temperature at 6:00 PM = 0oC + (-2oC) = - 2oC


Temperature at 7:00 PM = - 2oC + (-2oC) = - 4oC


Temperature at 8:00 PM = - 4oC + (-2oC) = - 6oC


Temperature at 9:00 PM = - 6oC + (-2oC) = - 8oC


Hence,


The temperature will be 8oC below zero at 9:00 PM


Now,


Change in temperature in 12 hours = - 2oC × 12


= - 24oC


Also,


At midnight the temperature will be = 10 + (-24)


= - 14oC


Hence,


The temperature at midnight will be 14oC below zero

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