Question

The temperature is changing at a constant rate of –0.75ºC per half hour. At 6:45 PM, the temperature was –4.6ºC. At what time was the temperature –2.1ºC? Be sure to include AM or PM in your answer.

Answer 1

5:05 PM

Explanation:

Each 30 minutes, we have a change of -0.75

So in an hour , we will have a change of -0.75 * 2 = -1.5

since -2.1 is greater than -4.6, this indicates that it was a time before 6:45 PM

so, let us find the temperature drop

That would be;

-2.1-(-4.6) = -2.1 + 4.6 = 2.5

So let us find the number of half hours

That would be;

2.5/0.75 = 3 1/3 half hours

3 half hours is 90 minutes

1/3 half hour is 1/3 * 30 = 10 minutes

Total number of minutes is;

90 + 10 = 100 minutes

So let us count 100 minutes before 6:45 PM

120 minutes before would be;

4:45 PM

but we want 100 minutes, so we have to add 20 minutes

That would be;

4:45 PM + 20 minutes

= 4:65 which is 5 : 05 PM