Writing Numeric Expressions

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Objective

SWBAT write and interpret simple expressions that record operations with numbers.

Big Idea

Expressions can be used to represent a mathematical or real-world problem using numbers and symbols to make meaning of a problem and understand problems.

Think About It

7 minutes

To begin the lesson I will ask my students work independently on the Think About It problem. After a few minutes of work time. I cold call one student to share his/her expression. 

I expect some of my students may be thrown by a subtraction expression that would result in a negative number, if evaluated.  My students won't learn to add and subtract integers until 7th grade, but they still have the tools to reason about this expression.  When the confusion inevitably surfaces, I remind students of the work we did in the Integers Unit.  

Some students are going to want to evaluate this expression (and the expressions throughout the lesson).  It's important that they're responding to what the question has asked of them, so I make sure to highlight during our discussion that they should not find the actual temperature on Monday.  

Intro to New Material

15 minutes

To start the Intro to New Material section, I have students fill in the notes for an expression.  I want them to record that an expression is a math phrase with symbols and numbers without an equal sign.

We'll then take a look at Example 1.  I give students 2 minutes to turn to their partners to read the problem and come up with an expression to represent the scenario.  I'll ask for volunteers to share the expression, and then will ask the class if any pair wrote down an different expression.  I'll continue to solicit expressions from the class, so long as there are hands in the air.  As you can see in this example, there are a number of possible expressions to represent this problem.  I want students to think about the multiple ways they can create a correct representation.

For Example 2, I'll display '14 - 35' and '35-14' on the board.  I'll ask students to clap once when I point to the expression they think is the correct expression for this problem.  I'll be a common error for 'less than' expressions for students to put the terms in the wrong order; I do expect some students to incorrectly clap when I point to '14-35.'  I'll as a student who correctly clapped for '35-14' to explain his/her thinking.  I'm looking for a student to articulate that we are starting with 35 and subtracting 14 from 35.  

 

Partner Practice

15 minutes

Students work in pairs on the Partner Practice problem set.  As students work, I circulate around the classroom and check in with each group.  I am looking for:

  • Are scholars correctly translating the verbal expression into numerical form?
  • Are students annotating the problems?
  • Are students selecting the correct operation?

I am asking:

  • Will the expression have the same answer if you changed the order of the terms?
  • How did you know which operation to use?
  • How did you know to order the numbers as you did?
  • What does the number represent in this problem?
  • What amount are you starting with?
  • Do you have to perform multiplication/division?
  • Do you have to perform addition/subtraction?
  • What would happen if you reversed the order of the expression? Would the expression still correctly represent the context?

Some of my students with the lowest reading levels may need some support in this lesson.  My student partner pairings already take reading level into account.  You can also choose to provide some students with the support of a list of 'key words,' like the one found here.  I've made the decision to not provide a resource like this to all of my students, because I want to them to really take the time to read, understand, and annotate each problem.   

Independent Practice

15 minutes

Students work on the Independent Practice problem set.  As they work, I will circulate around the room and check on what they're writing.  These are the steps that I expect students to use as they write their expressions:

1)      Read and annotate.

2)      Use a variable to represent unknowns and digits/operations for different values.

3)      Define the variable.

4)      Identify what amount you are starting with.

5)      Determine the operation performed on the starting amount.  Translate.

6)      Check by restating and comparing to the written expression.  

As I circulate, I have with me an answer key.  I can quickly scan my answers for Problems 3- 12, and compare to what students have written.  I'll ask individual students to explain to me their thinking for Problem 13.

 

Closing and Exit Ticket

10 minutes

After independent work time, I have students come back together to share out their work.  I ask students to flash me their responses for Problems 19-27.  My students have dry-erase sleeves, where they can write their expression and show me.  White boards would also work! The idea here is for me to be able to get some quick date from all students, in a way that's engaging for kids.  I won't ask students to show me all 8 answers - I'll pick a few from the set.

Students then independently complete the Exit Ticket to close the lesson.