Math Mission Teacher Guide
Math Mission Guide
Subject: Tier 2 Intervention - Addition & Subtraction within 100
Standard 2.NBT.5
Mission Objective
Students will fluently add and subtract within 100 by decomposing numbers, using number bonds, and applying place value strategies (adding/subtracting tens and ones).
Lab Materials
- Base-ten blocks (tens and ones)
- Double ten-frames & counters
- Dry-erase markers & personal boards
- Number Bonds & Blocks Worksheet
1
Warm-Up: Ten-Frame Flash (5 mins)
Flash a partially filled double ten-frame (e.g., 14). Ask students:
- "How many tens? How many ones?"
- "How many more to make 20?"
2
I DO: The Break-Apart Strategy (10 mins)
Target Problem: 25 + 13
Model using Place Value Decomposition:
25 = 20 + 5
13 = 10 + 3
Sum: (20 + 10) + (5 + 3) = 30 + 8 = 38
Key Script: "I'm going to crunch these numbers into tens and ones. It's much easier to add friends like 20 and 10 first!"
3
WE DO: Guided Lab Work (15 mins)
Work through 48 - 14 using a Number Bond.
- Step 1: Write 48 in the top circle.
- Step 2: Take away the tens first (48 - 10 = 38).
- Step 3: Take away the ones (38 - 4 = 34).
4
YOU DO & DATA (10 mins)
Students complete the Number Bonds & Blocks Worksheet. Monitor for common errors like subtracting the smaller digit from the larger regardless of place (e.g., 42 - 15 = 33 because 5-2=3).
Scaffolding Strategies
| If student struggles with... | Try this Lab Hack... |
|---|
| Regrouping/Trading | Use physical base-ten blocks to physically "break" a ten into ten ones. |
| Subtracting Tens | Use a 100-chart and practice jumping up/down by 10. |
| Number Decomposition | Use part-part-whole mats with physical counters. |
Math Mission Worksheet
Lab ID: 2.NBT.5
Number Cruncher Lab
Mission Agent
Date
1
Addition: Break it Down!
Break the numbers into Tens and Ones to find the total sum.
34 + 25 = ___
34
Tens
Ones
25
Tens
Ones
Work Area:
42 + 16 = ___
42
Tens
Ones
16
Tens
Ones
Work Area:
2
Subtraction: Ten-Frame Takeaway
Draw circles for the first number. X them out for the second number!
28 - 14 = ____
45 - 21 = ____
Final Lab Report
Solve the problem below using ANY strategy you learned today. Show your work!
57 - 23 = ___
My Strategy Lab Area
Number Cruncher Slides
Laboratory Mission
Number
Crunchers Lab
Mastering Addition & Subtraction within 100
Mission Briefing
The Goal
Use place value to add and subtract numbers within 100 with speed and accuracy.
Lab Vocabulary
10
Decompose (Break apart)
Fluency (Smooth & Fast)
=
Strategy (A smart plan)
Lab Tool #1: Break-Apart
Adding Tens with Tens and Ones with Ones
42 + 26
40 + 20
Tens
2 + 6
Ones
CRUNCH!
60 + 8
68
Let's Crunch Together!
WE DO
35 + 14
"I have 3 tens and 1 ten...
I have 5 ones and 4 ones..."
Steps:
- 1 Add the Tens: 30 + 10 = 40
- 2 Add the Ones: 5 + 4 = 9
- 3 Crunch: 40 + 9 = 49
Lab Tool #2: Number Bonds
Taking away by parts (Subtraction)
56 - 12
"We start with the big number and take away the tens first, then the ones."
56
10 Tens
2 Ones
Lab Trial: Subtraction
WE DO
48 - 14
Step 1
48 - 10 = 38
Step 2
38 - 4 = 34
Total
34
Mission Accomplished!
You've mastered the Lab Tools for today. Now, grab your Mission Worksheet and complete your final lab report!
Step 1 Worksheet Part 1
Step 2 Worksheet Part 2
