# Lesson 2

Changing Temperatures

### Problem 1

1. The temperature is -2$$^\circ \text{C}$$. If the temperature rises by 15$$^\circ \text{C}$$, what is the new temperature?
2. 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?

### Solution

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### Problem 2

Draw a diagram to represent each of these situations. Then write an addition expression that represents the final temperature.

1. The temperature was $$80 ^\circ \text{F}$$ and then fell $$20 ^\circ \text{F}$$.
2. The temperature was $$\text-13 ^\circ \text{F}$$ and then rose $$9 ^\circ \text{F}$$.
3. The temperature was $$\text-5 ^\circ \text{F}$$ and then fell $$8 ^\circ \text{F}$$.

### Solution

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### Problem 3

Complete each statement with a number that makes the statement true.

1.  _____ < $$7^\circ \text{C}$$
2.  _____ < $$\text- 3^\circ \text{C}$$
3.  $$\text- 0.8^\circ \text{C}$$ < _____ < $$\text- 0.1^\circ \text{C}$$
4.  _____ > $$\text- 2^\circ \text{C}$$

### Solution

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(From Unit 5, Lesson 1.)

### Problem 4

Decide whether each table could represent a proportional relationship. If the relationship could be proportional, what would be the constant of proportionality?

1. 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
2. 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

### Solution

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(From Unit 2, Lesson 7.)

### 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?

### Solution

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(From Unit 4, Lesson 7.)