Problem
9. In City A, the temperature rises $9^{\circ}$ from 8 A.M. to 9 A.M. Then the temperature drops $8^{\circ}$ from 9 A.M. to 10 A.M. In City B, the temperature drops $5^{\circ}$ from 8 A.M. to 9 A.M. Then the temperature drops $4^{\circ}$ from 9 A.M. to 10 A.M. Model the changes in temperature for each city on these number lines. a. What expression represents the change in temperature for City $A$ ? b. What integer represents the change in temperature for City $A$ ? c. What expression represents the change in temperature for City B? d. What integer represents the change in temperature for City B? e. Which city has the greater change in temperature from 8 A.M. to 10 A.M.?
Solution
Step 1 ：The question is asking to represent the changes in temperatures on a number line for two cities. In City A, the temperature rises 9 degrees from 8 A.M. to 9 A.M. and then drops 8 degrees from 9 A.M. to 10 A.M. In City B, the temperature drops 5 degrees from 8 A.M. to 9 A.M. and then drops 4 degrees from 9 A.M. to 10 A.M. These changes in temperatures can be represented as +9, -8 for City A and -5, -4 for City B on a number line.
Step 2 ：The expression that represents the change in temperature for City A is \(9 - 8\).
Step 3 ：The integer that represents the change in temperature for City A is \(1\).
Step 4 ：\(\boxed{\text{The expression for the change in temperature for City A is 9 - 8 and the integer is 1.}}\)
