Set Splitters Worksheet
Math Discovery Numbers Within 5
Set Splitters Worksheet
Draw lines to break sets into two parts, then write the addition sentence.
Name:
Date:
EXAMPLE
Look at the 4 acorns. A line splits them into 3 and 1:
→
Part: 3 + Part: 1 = Whole: 4
1 Whole Set: 5 Strawberries
Draw a line between the strawberries to split them into 2 parts.
Write your two parts and complete the sentence:
=
5
2 Whole Set: 4 Friendly Fish
Draw a line between the fish to split them into 2 parts.
Write your two parts and complete the sentence:
=
4
3 Whole Set: 3 Shining Stars
Draw a line between the stars to split them into 2 parts.
Write your two parts and complete the sentence:
=
3
4 Whole Set: 5 Little Ladybugs
Count each group separated by the dashed line.
Write the two parts and the sum:
=
💡 Key Math Idea: When we split a whole group, the two parts put together still equal the whole number!
Page 1 of 2
Part 2: Decomposing Practice
Split Two Ways & Draw to Explain
Name:
Discover that a number can be broken apart in more than one way!
A Split the Same Set in 2 Different Ways! (Target: 4)
Whole = 4
Draw a vertical line to split Way 1. Then find a different way to split Way 2!
Way 1
= 4
Way 2 (Different Split)
= 4
B Draw & Explain: Break Apart 5
Draw Your Thinking
Story: Leo has 5 toy cars. Some are in the garage and some are on the road. Draw the two parts!
Part 1: In the Garage
Count:
Part 2: On the Road
Count:
Addition Sentence:
=
5
Explain: "I split 5 into and because ."
C Math Detective: The Hidden Part!
Brain Teaser
There are 5 buttons in all. 2 buttons are outside the mystery box. How many buttons are hidden inside the mystery box?
Number Sentence: 2 +
= 5
●●
●●
?
Draw hidden buttons in the box
Self Check: Did both parts add up to the whole group? ⭐ Page 2 of 2
Set Splitters Lesson Plan
Teacher Guide Grades K–1 • Operations & Algebraic Thinking
Set Splitters Lesson Plan
Decomposing Pictured Sets Within 5 & Connecting to Addition Equations
Duration: 45 Mins
Focus: Numbers to 5
CCSS: K.OA.A.3 • 1.OA.B.4
🎯 Core Objective
Students will decompose pictured sets of up to 5 into two parts and write the matching addition equation (\(a + b = c\)).
📦 Materials
- • 5 two-color counters per student
- • 1 opaque cup per pair
- • Set Splitters Worksheet
- • Dry-erase boards & markers
💬 Vocabulary
Whole: total count in set.
Part: one group after splitting.
Decompose: break apart into parts.
WATCH OUT Common Student Misconceptions & In-the-Moment Teacher Fixes
Misconception: Splitting changes the total count.
Students recount one part and believe the other items "vanished" or the set is no longer 5.
✓ Teacher Fix: Have students physically push the parts back together to prove the total remains 5.
Misconception: Only one way to split a number exists.
Students assume 4 can only ever be \(2 + 2\).
✓ Teacher Fix: Show Page 2 of worksheet side-by-side to highlight \(3 + 1\) vs \(2 + 2\).
Lesson Sequence • Part 1: Exploration & Modeling
18 Minutes
Phase 1: The Magic Cup Hook (Warm-Up • 8 Mins)
Engage
Teacher Script: "Mathematicians, look at my hand. I have 5 yellow counters. Count with me: 1, 2, 3, 4, 5! Now close your eyes... Abracadabra!"
Place 2 counters under an upside-down cup and leave 3 on the table. "Open your eyes! How many can you see on the table? (3!) But remember, our whole set was 5. How many are hiding in the cup?"
Teacher Note: Record student thinking on chart paper: "3 outside + 2 hidden = 5 in all!" Connect the words part, part, and whole.
Phase 2: Direct Instruction & Modeling (I Do • 10 Mins)
Model
Display 4 magnets or draw 4 simple apples on the board.
- Step 1: Count the Whole. Point to each apple and write "Whole = 4" above them.
- Step 2: Draw the Splitter Line. "Today we are Set Splitters! Watch as I draw a vertical line right between apple 3 and apple 4."
- Step 3: Name the Parts. "On the left side, we have Part 1: 3 apples. On the right side, Part 2: 1 apple."
