Interpreting Negative Numbers Lesson Plan

Warm-up Activity

Start the class with a warm-up activity that will get students to start thinking about negative numbers in a real world context. Hand out the warm-up activity worksheet to each student. They may work with a partner if you would like. Have them work through this activity for a few minutes and then go over it as a class.

This activity is fun because students get to be creative and draw a thermometer to show the temperatures in Banff, Canada. Ask `1-2` students to come to the board to draw a thermometer. They are likely to show `4℉` below zero as `-4℉` and `4℉` above zero as `+4℉`. Talk about how they decided which would be the colder day. Ask students how a thermometer is similar to a number line.

Exploring elevation

Display this slide with a really silly picture of mountains and sea with hikers, boats, and fish. Students always have a good laugh at this picture… at my expense! But then we start talking about what this has to do with positive and negative numbers. 

I ask them to guess where zero would be in this picture. Where would be the positive numbers? And what about the negative numbers? We also try to guess the actual values where the hiker and the fish are likely to be. I then ask students to translate this picture into an open number line. To students, it makes sense that the number line should be vertical. Here is a drawing they are likely to make.

Then talk about the altitude of various places they know. Along with them do some research on what locations in the US are below sea level and are not under the sea. Talk about why that is possible and what sea level actually means. What locations are way above sea level? Do the same for the whole world.

Understanding negative numbers in the context of money 

Ask students to share their ideas about bank accounts. What do bank accounts have to do with negative numbers? Talk about deposits and withdrawals and what that means. Students will be astonished to learn that banks will allow you to withdraw more than what is in your account. Explain to them that it is called overdraft.  

It is a good idea to share some words that go with signed numbers. Students don’t need to know the formal definition; it is more important that they have an understanding of the words and how they related to positive and negative numbers.

Class practice

Take this first example step by step, using the transitions in the slideshow. First, ask students to identify the sign. You can ask students what part of the problem explains whether the value is positive or negative. Then, write the value with a negative sign. We’ll also include the units.

Display the next slide for students and ask them to follow the same two steps. Then reveal how you thought about it.

The slideshow contains two more example problems to complete as a whole class. Follow the same procedure as the previous examples and allow students to point out what about the problem helps us decide if the value will be positive or negative.

Whiteboard activity

Pass out whiteboards to students and play the whiteboard practice game with a few problems for students to try on their own. Give students a few minutes to think about each problem and then have students hold up their white boards in front of them for you to check. Have students volunteer to explain their answers for each one before moving on. There are a total of four additional problems to practice.