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addition

Adding three numbers

Look for friendly pairs and number bonds before adding.

Quick answer

Adding three numbers is easy when you find friendly pairs first. Look for numbers that add up to 10 or 5, then add the third number.

Learning outcome

By the end of this page, you will be able to add three numbers together by looking for pairs that make 10, 5, or other friendly numbers first. Success signs:
  • You can spot which two numbers make a friendly pair
  • You can add the third number quickly
  • You can use this strategy to solve addition problems
  • You can explain why this strategy works

Why this matters

Adding three numbers is part of your everyday maths. When you are shopping and buy three items, or when you play a game and score points in three rounds, you need to add three numbers together. This strategy helps you do it faster and more accurately. It also helps you get ready for bigger maths problems in school.

How it works

Adding three numbers means you have three groups of things to count. You can use a helpful strategy to make it easier:
  1. Look at all three numbers
  2. Find two numbers that make a friendly pair (like 5 + 5 = 10 or 3 + 2 = 5)
  3. Add the third number to that pair
This strategy works because it breaks the problem into smaller, easier parts.

Examples you can see

Let's look at some examples to help you understand. Example 1: Add 4 + 3 + 6 Step 1: Look at the numbers: 4, 3, 6 Step 2: Find a friendly pair: 4 + 6 = 10 Step 3: Add the third number: 10 + 3 = 13 So, 4 + 3 + 6 = 113 Example 2: Add 2 + 8 + 5 Step 1: Look at the numbers: 2, 8, 5 Step 2: Find a friendly pair: 2 + 8 = 10 Step 3: Add the third number: 10 + 5 = 15 So, 2 + 8 + 5 = 15 Example 3: Add 7 + 3 + 9 Step 1: Look at the numbers: 7, 3, 9 Step 2: Find a friendly pair: 7 + 3 = 10 Step 3: Add the third number: 10 + 9 = 19 So, 7 + 3 + 9 = 19

Try it as a mini adventure

Adventure: The Treasure Hunt You are going on a treasure hunt! You have three clues to follow, and each clue gives you a number of steps to walk. Clue 1: Walk 4 steps forward Clue 2: Walk 3 steps forward Clue 3: Walk 6 steps forward How many steps do you walk in total? Step 1: Look at the numbers: 4, 3, 6 Step 2: Find a friendly pair: 4 + 6 = 10 Step 3: Add the third number: 10 + 3 = 13 So, you walk 13 steps in total. You can try this with your family. Give each other clues and see who can find the most friendly pairs!

Common mistakes

  • Mistake: Adding all numbers in order without looking for pairs first.
    Why it happens: Some children think they must always add from left to right.
    Fix: Look for pairs that make 10 or 5 first, then add the third number.
  • Mistake: Forgetting to add the third number after making a pair.
    Why it happens: Kids get excited when they find a pair and forget the next step.
    Fix: Remember: Find a pair, then add the third number.
  • Mistake: Thinking 10 + 3 = 12 instead of 13.
    Why it happens: Confusion with counting or number bonds.
    Fix: Use your fingers or a number line to check.

Parent and carer guide

Parents and carers, here are 5 ways you can help your child learn to add three numbers:
  1. Use everyday situations: When shopping, ask, "If you buy 2 apples, 3 bananas, and 4 oranges, how many pieces of fruit do you have?"
  2. Play games: Use dice or cards to make three numbers and add them together.
  3. Count together: Make a game where you find pairs that make 10 and then add the third number.
  4. Use visual aids: Draw or use objects to show how numbers can be grouped.
  5. Encourage checking: After adding, ask your child to count again or use a number line to double-check.

Practice questions

  1. What is 3 + 7 + 2? Answer: 12
  2. What is 5 + 4 + 5? Answer: 14
  3. What is 6 + 3 + 4? Answer: 13
  4. What is 1 + 9 + 5? Answer: 15
  5. What is 8 + 2 + 7? Answer: 17
  6. What is 4 + 6 + 3? Answer: 13
  7. What is 2 + 8 + 1? Answer: 11
  8. What is 9 + 1 + 3? Answer: 13
  9. What is 5 + 5 + 2? Answer: 12
  10. What is 7 + 3 + 8? Answer: 18

FAQ

What does it mean to add three numbers?

Adding three numbers means you have three groups of things to count and you add them all together.

Why do we look for pairs first?

Looking for pairs first makes the problem easier because it breaks the big addition into smaller, easier parts.

Can I use this strategy with any three numbers?

Yes! This strategy works with any three numbers, but it's most helpful when you can make a pair that makes 5 or 10.

What if I can't find a friendly pair?

You can still add the numbers in order, but the friendly pair strategy makes it faster and easier.

How can I practice this at home?

You can practice by counting objects, playing games, or solving problems with your family. Try to find pairs that make 5 or 10 first.