Missing Addend

Grade 1 · mathematics · 84 practice problems · read aloud

🔊 Listen to this explanation

🧩 What is a Missing Addend?

A missing addend is a number that is missing from an addition sentence. We use it to find out "how many more" we need to reach a total. It's like a fun number puzzle! 🕵️‍♀️

How to Solve a Missing Addend Problem

  1. Look at the problem: You will see a total and one part of the addition.
  2. Think about what's missing: Ask yourself, "What number do I add to the part I know to get the total?"
  3. Count up or subtract: You can count up from the known number to the total, or you can subtract the known number from the total.
  4. Check your answer: Add the two parts together to see if they make the total!

Visual Examples

Example 1: 5 + ? = 8

We know one part is 5 and the total is 8. Let's count up from 5: 5...6, 7, 8. That's 3 more! So, 5 + 3 = 8. ✅

Example 2: ? + 4 = 10

We know one part is 4 and the total is 10. Let's subtract: 10 - 4 = 6. So, 6 + 4 = 10. ✅

⚠️ Common Mistakes

  • Adding the two numbers you see: If the problem is 3 + ? = 9, don't add 3+9! Instead, think about what goes with 3 to make 9.
  • Forgetting to check: Always add your answer back into the problem to make sure it's correct.

🌟 Tips & Tricks

  • Use your fingers: Start with the number you know and put up fingers until you reach the total. The number of fingers is your answer!
  • Draw pictures: Draw the total number of circles, then cross out the number you know. The ones left are your missing addend.
  • Fact Families are your friends: If you know 2 + 3 = 5, then you also know 5 - 2 = 3 and 5 - 3 = 2.

How to Practice

  • Play "How many more?" games. (e.g., "I have 4 stickers. I need 7. How many more do I need?")
  • Use small toys or blocks to act out the problems.
  • Ask a grownup to give you simple missing addend problems throughout the day!

Practice problems

6 of the 84, worked through step by step — try them before opening the answer.

1 7 + ? = 12

Hint: Think about what number you need to add to the first number to reach the total.

Show the answer

Answer: 5

  1. The goal is to find the number that goes in place of the "?". We know that adding 7 to this unknown number gives 12.
  2. To find the unknown number, we can subtract 7 from both sides of the equation. This is because subtraction is the opposite of addition.
  3. Perform the subtraction: 12 − 7 = 5.
  4. So the unknown number is 5. We can check: 7 + 5 = 12, which is correct. ANSWER: 5

We start with the equation: 7 + ? = 12.

2 7 + ? = 15

Hint: Think about what number you need to add to the first number to reach the total.

Show the answer

Answer: 8

  1. Let the unknown number be x. So we write: 7 + x = 15
  2. To find x, we need to get x alone on one side of the equation. Since 7 is added to x, we do the opposite operation: subtract 7 from both sides.
  3. Subtract 7 from both sides: 7 + x - 7 = 15 - 7
  4. Simplify both sides: On the left: 7 - 7 = 0, so we have x. On the right: 15 - 7 = 8. So x = 8.
  5. Check: Replace x with 8 in the original equation: 7 + 8 = 15. That is correct. Therefore, the missing number is 8.

We are solving: 7 + ? = 15

3 8 + ? = 15

Hint: Think about what number you need to add to the first number to reach the total

Show the answer

Answer: 7

  1. We know 8 + ? = 15
  2. To find the missing number, think about what number added to 8 equals 15
  3. Start from 8 and count up to 15: 9, 10, 11, 12, 13, 14, 15
  4. That's 7 more numbers
  5. So 8 + 7 = 15

The answer is 7.

4 8 + ? = 14

Hint: Think about what number you need to add to the first number to reach the total.

Show the answer

Answer: 6

  1. The problem is 8 + ? = 14. This means we need to find the missing number that, when added to 8, equals 14.
  2. One way to find the missing number is to subtract 8 from 14.
  3. 14 - 8 = 6.
  4. Check: 8 + 6 = 14, which is correct. The missing number is 6.

5 8 + ? = 17

Hint: Think about what number you need to add to 8 to get 17

Show the answer

Answer: 9

  1. Start with the equation 8 + ? = 17
  2. To find the missing number, subtract 8 from 17
  3. 17 - 8 = 9
  4. Check: 8 + 9 = 17

The answer is 9.

6 15 - ? = 8

Hint: Think about what number you need to take away from 15 to get 8

Show the answer

Answer: 7

  1. We know that 15 minus some number equals 8
  2. Think about what number plus 8 equals 15
  3. 8 + 7 = 15
  4. So 15 - 7 = 8

The answer is 7.

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