Decimal Alignment Worksheet
Math Intervention Lab Place Value • Alignment Focus
Decimal Alignment Worksheet
Name:
Date:
Goal: Line Up the Dots!
The Golden Decimal Wall
Decimals must always stack on the line. Fill empty spaces on the right with a 0 so every column has a partner!
T O • t h
2 4 . 3 0
+ 1 5 . 2 5
3 9 . 5 5
1 Step 1: Compute Pre-Aligned Sums
Use regrouping boxes at the top if carrying
Problem 1 23.4 + 14.2 No Regrouping
TO•t
23•4
+14•2
•
Problem 2 35.8 + 17.6 Regrouping
TO•t
35•8
+17•6
•
Problem 3 42.50 + 8.35 Hundredths
TO•th
42•50
+8•35
•
Problem 4 16.8 + 5.45 Ghost Zero!
TO•th
16•80
+5•45
•
2 Step 2: You Align & Solve — Write digits in the columns
Keep decimals on the teal track!
Problem 5 14.6 + 9.25 Annex 0 to 14.6
TO•th
•
•
Problem 6 28.35 + 7.8 Annex 0 to 7.8
TO•th
•
•
Decimal Alignment Intervention • Page 1: Guided Addition Page 1 of 2
Intervention Support • Regrouping Focus
Decimal Subtraction & Word Scenarios
Student Name:
Warning: Never Subtract From Empty Space!
If the top number has missing decimal digits, you must write .0 or .00 first before you can borrow!
Whole number 50:
50 → 50.00
Now you can borrow!
3 Step 3: Subtraction with Pre-Placed Zeros
Borrow across columns into the top boxes
Problem 7 46.5 - 18.2 Borrow from T
TO•t
46•5
−18•2
•
Problem 8 34.50 - 16.28 Zero in Top!
TO•th
34•50
−16•28
•
Problem 9 50.00 - 23.45 Across Zeros
TO•th
50•00
−23•45
•
Problem 10 27.3 - 9.64 Ghost Zero!
TO•th
27•30
−9•64
•
4 Step 4: Word Scenarios — Use the pre-aligned grid to find the answer
Scenario A: Shopping Trip Money
Liam has $20.00. He buys a notebook for $6.45. How much change will Liam get back?
Change:
TO•th
$20•00
−6•45
•
Scenario B: Board Length Measurement
A carpenter has a board measuring 15.8 inches. She cuts off 4.25 inches. How many inches of board are left?
Remaining length: in
TO•th
15•80
−4•25
•
Decimal Alignment Intervention • Page 2: Subtraction & Applications Page 2 of 2
Decimal Alignment Answer Key
Teacher Guide Answer Key
Decimal Alignment — Solutions
Master Key with Regrouping Marks
Intervention Diagnostic Cues
Common error: Students lining up digits to the right (like whole numbers). Ensure they locate the decimal point first before writing any digits.
Key Focus for Stage 1: • Dropping decimal directly into sum
• Carrying 1s into correct place columns
1 Step 1: Pre-Aligned Sums — Solutions
Red values indicate student entries
Problem 1 23.4 + 14.2 Sum = 37.6
TO•t
23•4
+14•2
3 7 • 6
Problem 2 35.8 + 17.6 Sum = 53.4
TO•t
1 1
35•8
+17•6
5 3 • 4
Problem 3 42.50 + 8.35 Sum = 50.85
TO•th
1
42•50
+8•35
5 0 • 8 5
Problem 4 16.8 + 5.45 Sum = 22.25
TO•th
1 1
16•80
+5•45
2 2 • 2 5
2 Step 2: You Align & Solve — Model Placements
Check that students annex zeros in empty places
Problem 5 14.6 + 9.25 Sum = 23.85
TO•th
1
14•60
+9•25
2 3 • 8 5
Problem 6 28.35 + 7.8 Sum = 36.15
TO•th
1 1
28•35
+7•80
3 6 • 1 5
Decimal Alignment Teacher Key • Page 1 Solutions Page 1 of 2
Teacher Facilitation • Regrouping Focus
Decimal Subtraction — Answer Key
Answer Key
Borrowing Misconception Alert
In Problem 8 and 10, watch for students writing \( 0 - 8 = 8 \) instead of borrowing. Remind them: "More on the floor? Go next door and get 10 more!"
Whole Numbers to Decimals: \( \$20 \rightarrow \$20.00 \) (two zeros)
\( 50 \rightarrow 50.00 \) before borrowing
3 Step 3: Subtraction with Regrouping Marks
Borrowing values shown in top row
Problem 7 46.5 - 18.2 Diff = 28.3
TO•t
3 16
46•5
−18•2
2 8 • 3
Problem 8 34.50 - 16.28 Diff = 18.22
TO•th
2 14 4 10
34•50
−16•28
1 8 • 2 2
Problem 9 50.00 - 23.45 Diff = 26.55
