🧩 Missing Numbers and Grouping in Addition

What you’ll learn

1. The Missing PieceFind a missing number in an addition sentence, like □ + 9 = 14, by subtracting.In puzzles like 8 + □ = 10, a number is hiding, and a ten frame's empty spots can reveal it. For bigger mysteries like □ + 9 = 14, subtract to undo the adding: 14 − 9 = 5. Always check your answer by putting it back in: 5 + 9 = 14.
2. Subtraction Is a PuzzleSee that a subtraction like 10 − 8 is the same as the missing-addend question 8 + ? = 10.Every take-away is secretly a missing-number puzzle: 10 − 8 asks 'what plus 8 makes 10?' That means you can solve subtraction by climbing UP — from 8 to 10 is 2 steps, so 10 − 8 = 2. Thinking in addition often makes subtracting faster and friendlier.
3. Three Numbers, Your ChoiceKnow that when adding three numbers, any two can be added first and the total stays the same.With a sum like 2 + 6 + 4, you can group any two numbers first: (2 + 6) + 4 and 2 + (6 + 4) both make 12. The total never changes — only the path does. That freedom lets you pick whichever pair feels easiest.
4. Hunt for TenUse grouping to find pairs that make ten first, like solving 2 + 6 + 4 as 2 + 10 = 12.Since grouping is your choice, hunt for pairs that make 10 first. In 2 + 6 + 4, grab 6 + 4 = 10, then add 2 to get 12. The same trick cracks 5 + 3 + 5 (the fives make ten, total 13) and 3 + 4 + 6 (four and six make ten, total 13).

Questions this course answers

Grounded in trusted sources

• Khan Academy Kids
• PBS Kids — early math
• NAEYC — early math learning
• Britannica Kids

Every Wunder lesson is built from real, reputable sources — never invented.

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