Lesson 14 Think Before You Subtract
Let’s think about decomposing before we subtract.
Warm-up Which One Doesn’t Belong: Blocks and Blocks and Blocks
Which one doesn’t belong?
Activity 1 Agree to Disagree
Tyler and Clare are subtracting by place to find the value of
The diagrams show each student’s first step.
What is the same about Tyler and Clare’s diagrams? What is different?
Work together to complete Tyler’s way and Clare’s way to find the value of
What do Tyler and Clare’s diagrams look like after the last step? What is the same about these diagrams? What is different?
Activity 2 Sort and Subtract
Here is a base-ten diagram for 341.
Andre wants to use diagrams and subtract by place to find the value of
. He says he will decompose a ten and a hundred to subtract. Why do you think he said that?
Andre only wants to use a diagram to subtract by place if he will decompose a unit. Help Andre sort the expressions into groups. If you are not sure, use base-ten blocks or a diagram to help.
decompose 2 units
decompose 1 unit
do not decompose
Find the value of 1 expression from each group. Show your thinking.
Jada is finding the value of