Block Subtractor Slides
Block Subtractors
Subtracting Numbers Within 50
Tens Ones
Today's Mission
Goal
We will use Base-10 Blocks to subtract numbers up to 50!
You Need:
- Base-10 Blocks
- Place Value Mat
- Whiteboard & Marker
Warm-Up Challenge
Can you build these numbers on your mat?
34
41
19
Watch and Learn
Embedded media
Get ready to pause and build!
Pause & Think
Which side do we
start with?
TENS
ONES
Partner Power
A Partner A
Build the first number on the mat using blocks.
B Partner B
Take away the blocks for the second number.
Both partners write the Vertical Equation on your whiteboards!
Level 1 Problems
36 - 12
48 - 24
29 - 15
Time to Chat!
"Why is it helpful to use the blocks before just writing the numbers?"
Bonus Level
THE TRICKY ONE
42 - 15
Try it with your blocks...
Why does this one feel different?
Block Subtractor Facilitation Guide
Block Subtractor
Teacher Facilitation Guide
Subject: Math
Grade: 1st Grade
Duration: 40 Minutes
Learning Objective
Students will be able to subtract numbers within 50 without regrouping using concrete manipulatives (Base-10 blocks) and record their work using the vertical algorithm.
Materials Needed
- Base-10 Blocks (Rods & Cubes)
- Place Value Mats (Tens/Ones)
- Individual Student Whiteboards
- Dry Erase Markers
1
Warm-Up: Build It! (5 min)
Goal: Build familiarity with representing numbers with blocks.
Instruction: Give students baggies of blocks. Call out numbers and have them build them on their mats.
34 41 19
2
Video & Discussion (5 min)
Video: "Subtraction Within 50 Without Regrouping"
| Time | Action / Question |
|---|
| 0:28 | Pause: Ask students to predict where to write 45 and 23 on the notebook. |
| 0:43 | Pause: "Which column do we always start with? The tens or the ones?" |
| 0:52 | Pause: Count the remaining blocks on screen together before the narrator reveals the answer. |
| 1:14 | Pause: Read the full number represented by the remaining blocks (2 tens and 2 ones). |
3
Main Activity: Partner Subtract (20 min)
Step 1: Partner A builds the starting number.
Step 2: Partner B "takes away" the rods and cubes for the second number.
Step 3: Both partners write the vertical equation on their whiteboards.
Problem 1 36 - 12
Problem 2 48 - 24
Problem 3 29 - 15
4
Closure & Extension (10 min)
Discussion Prompt:
"Why is it helpful to use the blocks before just writing the numbers?" (Look for: "It helps me see the taking away," "I can see the tens and ones clearly").
Extension Challenge
Try 42 - 15. Ask: "What happens when we try to take away 5 ones from only 2 ones? Why does this get tricky?" This seeds the idea for regrouping.
Base-10 Blocks Place Value Column Method Subtract
Block Subtractor Practice Worksheet
Block Subtractors
Explorer Name
Date
Build the first number with blocks. Take away the blocks for the second number. Write the answer!
01
3 6
- 1 2
02
4 8
- 2 4
03
2 9
- 1 5
04
4 5
- 2 3
05
3 7
- 1 6
!!
The Tricky One
42 - 15 = ?
Try to solve it.
Why is this one harder to do with blocks?
Tens
Ones
