Question

In a science experiment, the temperature of a substance is changed from 42 °F to −54 °F at an average rate of −12 degrees per hour. Over how many hours does the change take place?

A 8 hours B
1
8
hour
C −8 hours D 1 hour

Answer 1

Its 8hrs

Explanation:

Answer 2

Remark

There are a couple of ways to do this. The easiest is to take the number of degrees between 42 and - 54 and divide by 12.

Method

the number of degrees is abs(42) + abs(-54) = 42 + 54 = 96

Now divide by 12

Hours = 96 / 12 = 8 hours. I think the answer is A.