Mental Addition Strategies

Free sample questions, a clear explanation, and 5 practice skills with an AI tutor that guides without giving the answer away.

Be a Mental Math Superhero!

Have you ever built with LEGOs? It's much easier to build a big castle if you first click together groups of 10 bricks. Adding numbers in your head is just like that! We can be super fast and smart by looking for ways to make "friendly tens." Let's learn some amazing tricks to make your brain a math calculator!

Trick #1: Making a Ten with Friends

Let's add 8 + 6. It's faster if we make a ten first! We know 8 needs 2 more to become 10. So, we can borrow a 2 from the 6.

8 + 6

is the same as

8 + 2 + 4

which is

10 + 4 = 14

Trick #2: Adding Bigger Numbers

What about 27 + 5? We can use the same trick! Get 27 to the next friendly ten, which is 30.

27 needs 3 to make 30. So we split the 5 into a 3 and a 2. Now it's 27 + 3 + 2, which is 30 + 2 = 32. Wow!

For two big numbers like 43 + 35, just add the tens, then the ones!

Add the tens: 40 + 30 = 70
Add the ones: 3 + 5 = 8
Put them together: 70 + 8 = 78

Key Takeaway!

Making a "friendly ten" is your number one mental math superpower! Whether you're adding small numbers or big ones, always look for ways to make a 10. It makes adding so much easier and faster.

Your Secret Weapon: Number Bonds!

How do we know so quickly that 8 needs a 2 to make 10? Because of our amazing number bond knowledge! Knowing your "friends of 10" (like 1+9, 2+8, 3+7, 4+6, 5+5) is the secret key that unlocks all these mental math tricks. Practice them, and you'll be a true math wizard!

Sample questions

1. What is 8 + 4?

○ 11

○ 13

✓ 12

○ 10

Answer: 12 — Think about making 10 first! (8 + 2 + 2)

2. Find the sum of 7 + 6.

○ 10

○ 12

○ 14

✓ 13

Answer: 13 — Break apart the 6 to help 7 reach 10. (7 + 3 + 3)

3. What is 9 + 3?

○ 11

✓ 12

○ 13

○ 10

Answer: 12 — How much do you need to add to 9 to make 10? (9 + 1 + 2)

Skills in this topic

Add two 1-digit numbers using number bonds to make 10 (e.g., 7+5 = 7+3+2)
Add a 2-digit number and a 1-digit number mentally by counting on or making a ten
Add two 2-digit numbers mentally by adding tens then ones, or by compensation
Use mental strategies to add three or more 1-digit numbers
Describe how knowing number bonds helps you quickly add numbers in your head, giving an example

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