Question

The temperature at 4 a.m. was -13 degress F. The temperature was rising at a steady rate of 5 degrees an hour. At what time will the temperature be 12 degrees F?

Answer 1

Solution:-
Temperature at 4 AM = -13° F
Rate of temperature rising = 5° F
After one hour the temperature will be = (-13 + 5)° F
After two hours the temperature will be = (-13 + 10)° F
After three hours the temperature will be = (-13 + 15)° F
After four hours the temperature will be = (-13 + 20)° F
After five hours the temperature will be = (-13 + 25)° F
⇒ 12° F
So the time will be 4 AM + 5 hours = 9 AM.
AT 9 AM the temperature will be 12° F.

Answer 2

Initial Temperature at 4 am:  -13 °F
Final Temperature = 12°F

Rate of increase of Temperature = 5 °F/hour

Duration = amount of temperature to rise / rate
               = [12° - (-13°) ] / 5    hours 
               = 5 hours

So at  4 am + 5 hours = 9 am the temperature will be 12°F