Lesson 6Subtracting Rational Numbers
Learning Goal
Let’s bring addition and subtraction together.
Learning Targets
I can find the difference between two rational numbers.
I understand how to subtract positive and negative numbers in general.
Lesson Terms
- deposit
- withdrawal
Warm Up: Number Talk: Missing Addend
Problem 1
Solve each equation mentally.
Problem 2
Rewrite each addition equation as a subtraction equation.
Activity 1: Expressions with Altitude
Problem 1
A mountaineer is changing elevations. Write an expression that represents the difference between the final elevation and beginning elevation. Then write the value of the change. The first one is done for you.
beginning | final | difference | change |
---|---|---|---|
Are you ready for more?
Problem 1
Fill in the table so that every row and every column sums to 0. Can you find another way to solve this puzzle?
Activity 2: Does the Order Matter?
Problem 1
Find the value of each subtraction expression.
A | B |
---|---|
Problem 2
What do you notice about the expressions in Column A compared to Column B?
Problem 3
What do you notice about their values?
Lesson Summary
When we talk about the difference of two numbers, we mean, “subtract them.” Usually, we subtract them in the order they are named. For example, the difference of +8 and
The difference of two numbers tells you how far apart they are on the number line.
Notice that if you subtract them in the opposite order, you get the opposite number:
In general, the distance between two numbers