Stack And Add Slides
Grade 2 Math • Standard Algorithm
Place Value Power
Stack & Add!
Mastering 2-Digit Vertical Addition with Place Value Columns
No Regrouping Needed
Tens & Ones Alignment
Focus: Transitioning from Horizontal to Vertical Equations Step-by-Step Guided Lesson
The Big Idea
Why Do We Stack Numbers?
Horizontal Equation
\( 43 + 25 = \text{?} \)
It can be hard to match which digits belong to tens and which belong to ones across a long sentence!
Vertical (Stacked) Columns
TENS ONES
4 3
5
6 8
Stacking lines up friends with friends: Ones with Ones and Tens with Tens!
Key Takeaway: When place values line up in straight columns, addition becomes super fast and easy!
Standard Algorithm
The 3 Golden Rules of Stacking
1
Line Up Place Value
Write the first number on top. Stack the second number directly underneath so Ones sit under Ones and Tens sit under Tens.
Keep neat vertical columns!
2
Add the ONES First
Always begin on the right side! Add the two digits in the Ones column and write their sum directly below the line.
Always start on the right!
3
Add the TENS Next
Move to the left! Add the two digits in the Tens column and write the total under the line in the Tens spot.
Read the full 2-digit sum!
Chant with me: "Line 'em up straight! Start in the Ones! Finish in the Tens!"
Teacher Model
Let's Solve: \( 34 + 52 \)
Step-by-Step
Step 1: Build the Chart
Write 34 on top (\(3\) tens, \(4\) ones). Place 52 below (\(5\) tens, \(2\) ones).
Step 2: Add Ones First
\( 4 \text{ ones} + 2 \text{ ones} = \) 6. Write 6 in the ones spot!
Step 3: Add Tens Next
\( 3 \text{ tens} + 5 \text{ tens} = \) 8. Write 8 in the tens spot!
Tens (10s)
Ones (1s)
3 4
8 6
\( 34 + 52 = \) 86
Notice: Neither column added up to 10 or more! 8 tens and 6 ones equals 86
Skill Builder
Rewriting: Horizontal → Vertical
Your Worksheet Gives You:
\( 61 + 27 = \underline{\hspace{2cm}} \)
You will receive a blank Tens | Ones chart. Here is how to fill it in!
A
Put the first number 61 on the top line: 6 in Tens, 1 in Ones.
B
Put the plus sign + to the left of the bottom number.
C
Put the second number 27 underneath: 2 in Tens, 7 in Ones.
T (Tens) O (Ones)
6 1
8 8
\( 1 + 7 = 8 \) Ones • \( 6 + 2 = 8 \) Tens • Total = 88
Always double check: Are the digits directly above and below each other? Yes!
Guided Practice
Your Turn to Try!
Whiteboard / Think-Pair-Share
Problem A Rewrite & Solve
\( 45 + 31 = \text{?} \)
Tens Ones
45
+31
76
Ones: \( 5 + 1 = 6 \) • Tens: \( 4 + 3 = 7 \) → 76
Problem B Watch the 1-Digit Number!
\( 72 + 5 = \text{?} \)
Tens Ones
72
+05
77
The 5 is 5 ones, so it must go in the Ones column! → 77
Did you remember to add the ones first each time?
Math Detective
Spot the Stacking Mistake!
What Leo Did Equation: \( 53 + 4 \)
TO
53
+4-
93
Leo says: "\( 53 + 4 = 93 \)!" Why is this incorrect?
The Correct Fix Correct Alignment
TO
53
57
4 means 4 ones, not 4 tens! The true answer is 57!
Rule of Thumb: Single-digit numbers must always line up on the far right under the Ones column!
Independent Practice
Time to show your skills!
You're Ready to Stack!
Grab your worksheet and place value charts. Remember your 3 steps:
Step 1
Line Up Digits
Write Tens in the T column and Ones in the O column.
Step 2
Add the Ones
Add the right column first and record your answer.
Step 3
Add the Tens
Add the left column next to find the final total.
Keep your columns straight and clean! Happy Adding!
Stack And Add Worksheet
Stack & Add Worksheet
Rewrite Vertically & Solve • Place Value Alignment
Name:
Date:
How to Rewrite & Add
1. Line up place values: Write Tens under Tens (T) and Ones under Ones (O).
2. Add the ONES first, then add the TENS. Write your total in the equation!
Model
TO
24
59
\(4+5 = 9\)
\(2+3 = 5\)
1
Rewrite Vertically & Solve
Use the Tens (T) and Ones (O) place value charts.
1 Problem 1
\( 23 + 45 = \)
Rewrite in chart →
T O
2 Problem 2
\( 51 + 37 = \)
Rewrite in chart →
T O
3 Problem 3
\( 34 + 62 = \)
Rewrite in chart →
T O
4 Problem 4
\( 72 + 15 = \)
Rewrite in chart →
T O
5 Problem 5
\( 40 + 29 = \)
Rewrite in chart →
T O
6 Problem 6
\( 16 + 82 = \)
Rewrite in chart →
T O
Self-Check: Did you always add the ones column before the tens column? Page 1 of 2
2
Stack & Add Worksheet • Continued
Name:
Alignment Alert: When adding a 1-digit number (like 4 or 7), put it in the Ones (O) column!
Check Columns
2
Independent Rewrite & Solve
Keep your vertical columns straight and aligned!
7 Problem 7
\( 43 + 34 = \)
Rewrite in chart →
T O
8 Problem 8
\( 62 + 25 = \)
Rewrite in chart →
T O
9 Problem 9 Tricky!
\( 53 + 4 = \)
4 means 4 ones → Ones box!
T O
10 Problem 10
\( 70 + 18 = \)
Rewrite in chart →
Stack And Add Answer Key
Teacher Answer Key
Page 1 Solutions
Stack & Add Worksheet • Questions 1 – 6
Scoring: 2 pts each (1 pt align, 1 pt sum)
Grading Note: Award 1 point for placing the correct digits into the Tens (T) and Ones (O) columns, and 1 point for the accurate sum. Always verify that students added the Ones column first!
1
Solved Place Value Charts (Questions 1 – 6)
12 Points Possible on Page 1
Problem 1
\( 23 + 45 = \) 68
Ones: \(3+5=8\) • Tens: \(2+4=6\)
TO
23
68
Problem 2
\( 51 + 37 = \) 88
Ones: \(1+7=8\) • Tens: \(5+3=8\)
TO
51
88
Problem 3
\( 34 + 62 = \) 96
Ones: \(4+2=6\) • Tens: \(3+6=9\)
TO
34
96
Problem 4
\( 72 + 15 = \) 87
Ones: \(2+5=7\) • Tens: \(7+1=8\)
TO
72
87
Problem 5
\( 40 + 29 = \) 69
Ones: \(0+9=9\) • Tens: \(4+2=6\)
TO
40
69
Problem 6
\( 16 + 82 = \) 98
Ones: \(6+2=8\) • Tens: \(1+8=9\)
TO
16
98
Stack & Add Answer Key • Master Grading Copy Answer Key • Page 1 of 2
2
Answer Key • Questions 7 – 12
Master Scoring Guide
Key Alignment Check: Questions 9 & 11 feature 1-digit addends (\(4\) and \(7\)). Verify they sit under the Ones column!
Special Focus
2
Solved Place Value Charts (Questions 7 – 12)
12 Points Possible on Page 2
Problem 7
\( 43 + 34 = \) 77
Ones: \(3+4=7\) • Tens: \(4+3=7\)
TO
43
