At noon, the temperature in Promontory, California was

70°F. By midnight, the temperature had fallen to

40°F. What was the change in temperature over the 12-hour period?

Change in temperature is - 30°F

Step-by-step explanation:

Given:

Temperature in noon : 70°F

Temperature by mid-night : 40°F

The change in temperature is measured by subtracting the second temperature from 1st. If the temperature increased then the change is positive and if the temperature decreased then the change is negative.

So,

Here

Change in temp = Temp at mid-night - temp in noon

= 40 - 70 = - 30°F

Hence the change in temperature is - 30°F ...