Lesson 2
Changing Temperatures
Let's add signed numbers.
Problem 1
 The temperature is 2\(^\circ \text{C}\). If the temperature rises by 15\(^\circ \text{C}\), what is the new temperature?
 At midnight the temperature is 6\(^\circ \text{C}\). At midday the temperature is 9\(^\circ \text{C}\). By how much did the temperature rise?
Problem 2
Draw a diagram to represent each of these situations. Then write an addition expression that represents the final temperature.
 The temperature was \(80 ^\circ \text{F}\) and then fell \(20 ^\circ \text{F}\).
 The temperature was \(\text13 ^\circ \text{F}\) and then rose \(9 ^\circ \text{F}\).
 The temperature was \(\text5 ^\circ \text{F}\) and then fell \(8 ^\circ \text{F}\).
Problem 3
Complete each statement with a number that makes the statement true.
 _____ < \(7^\circ \text{C}\)
 _____ < \(\text 3^\circ \text{C}\)
 \(\text 0.8^\circ \text{C}\) < _____ < \(\text 0.1^\circ \text{C}\)
 _____ > \(\text 2^\circ \text{C}\)
Problem 4
Decide whether each table could represent a proportional relationship. If the relationship could be proportional, what would be the constant of proportionality?

The number of wheels on a group of buses.
number of buses number of wheels wheels per bus 5 30 8 48 10 60 15 90 
The number of wheels on a train.
number of train cars number of wheels wheels per train car 20 184 30 264 40 344 50 424
Problem 5
Noah was assigned to make 64 cookies for the bake sale. He made 125% of that number. 90% of the cookies he made were sold. How many of Noah's cookies were left after the bake sale?