The table shows the temperatures for one day in January in a city. Find the change in temperature between 8 AM and 6 PM. Write an integer to describe the change in temperature between 3 PM and 9 PM. Interpret this integer.
There are three parts to this question. The first part asks us to find the change in temperature between 8 AM and 6 PM. At 8 AM, the temperature was negative two degrees Fahrenheit. At 6 PM, it had increased to 11 degrees Fahrenheit. We need to calculate the difference between negative two and 11. If we consider the number line as shown from negative two to 11, there is an increase of two degrees from negative two to zero and an increase of 11 degrees from zero to 11. Two plus 11 is equal to 13. This means that the change in temperature between 8 AM and 6 PM is 13 degrees Fahrenheit, or plus 13.
The second and third parts of the question involved the change in temperature between 3 PM and 9 PM. At 3 PM, the temperature was 15 degrees Fahrenheit. Whereas at 9 PM, it had decreased to negative one degrees Fahrenheit. Once again, we can use a number line, this time to see how we get from 15 to negative one. To get from 15 to zero, we need to subtract 15. And to get from there to negative one, we need to subtract another one. Negative 15 minus one is negative 16. This means that the integer or whole number that describes the change in temperature from 3 PM to 9 PM is negative 16.
The final part of our question asks us to interpret this integer. As this is a negative number, we can conclude that the temperature has decreased by 16 degrees Fahrenheit. A positive integer would indicate an increase. And a negative integer, a decrease.