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K.2 Addition up to 10: type the missing number

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Understanding Missing Numbers in Addition

Missing number problems ask you to find the number that makes the addition sentence true. The number can be at the beginning, in the middle, or at the end of the sentence.

Example Problems:
  • [] + 3 = 5 → The missing number is 2
  • 4 + [] = 6 → The missing number is 2
  • 2 + 5 = [] → The missing number is 7
Helpful Hint

Think about what you need to add to the given number to reach the total. Counting on from the given number can help.

Using Number Lines to Find Missing Numbers

A number line helps you see the “jumps” needed to reach the total. Start at the first number and count forward until you reach the answer.

Example:
  • 4 + [] = 7 → Start at 4, jump forward: 5, 6, 7 → 3 jumps
  • [] + 2 = 5 → Start at 2, count backward from 5: 5, 4, 3 → The missing number is 3
Reminder

Each jump represents adding 1. Count carefully to make sure you land exactly on the total.

Checking with Objects

Using real or drawn objects can help confirm your answer. Put groups together to see if the total matches the problem.

Example:
  • [] + 3 = 6 → Try 3 red counters and see what number of blue counters makes 6 total → 3
  • 5 + [] = 8 → Start with 5 blocks, add until you have 8 → Added 3 blocks
Helpful Hint

Arrange objects in two clear groups so you can see both the starting number and the added amount.

Using Counting Strategies

Counting on is a quick way to solve missing number problems. Start from the larger known number and count until you reach the total.

Example:
  • 6 + [] = 9 → Start at 6: 7, 8, 9 → 3 counts
  • [] + 2 = 4 → Start at 2 and think “2 plus what makes 4?” → 2
Teacher Tip

Encourage students to say each number out loud when counting on. This reinforces number order and addition facts.

Practice and Review

Frequent practice helps make finding missing numbers faster and easier. Mix problems with the missing number in different positions.

Example Practice Set:
  • [] + 1 = 5
  • 7 + [] = 10
  • 2 + 4 = []
Helpful Hint

Try solving without objects once you feel confident. This builds mental math skills.