At 3 A.M. the temperature was 13 degree below zero. By noon, it had risen to 32. What was the average hourly increase in temperature?

The temperature at 3 A.M. was 13 degrees below zero, so it was -13 degrees.

By noon, the temperature had risen to 32 degrees.

To find the change in temperature: Change in temperature = Final temperature - Initial temperature Change in temperature = 32 degrees - (-13 degrees) Change in temperature = 32 degrees + 13 degrees Change in temperature = 45 degrees

Now, we want to find the average hourly increase. There are 9 hours from 3 A.M. to noon (3 A.M., 4 A.M., 5 A.M., 6 A.M., 7 A.M., 8 A.M., 9 A.M., 10 A.M., 11 A.M.), so we'll divide the change in temperature by 9:

Average hourly increase = Change in temperature / Number of hours Average hourly increase = 45 degrees / 9 hours

Now, simplify:

Average hourly increase = 5 degrees per hour

So, the average hourly increase in temperature is 5 degrees.

The correct answer is 5 degrees per hour.