# Finding the Unknown Number (in Addition) — Let's Practice!

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## Finding the Unknown Number in Addition – Introduction

Get a piece of paper and a pencil ready because today we're going to practise finding the unknown number in addition. It’s a cool trick that helps you figure out missing parts in maths problems. Ready to begin? Let's go!

## What Is Finding the Unknown Number in Addition?

Finding the unknown number in addition means using parts and the whole to find the missing number in an addition problem.

For example, if you know how many items you started with and how many you ended with, you can find out how many were added. Let’s practise this with some fun problems!

What does finding the unknown number in addition mean?
How do you find the unknown number?
Why do we use this method?

## Finding the Unknown Number in Addition – Example

Let's solve a problem to find the unknown number:

Problem

If Emma started with 7 bits of wood for her new project and ended up with 12, how many bits did she add?

Solution

Follow these simple steps to find the solution.

Step Explanation
Write the equation 7 + ? = 12
Count up from the part (7) to the whole (12) Count: 8, 9, 10, 11, 12
Find how many numbers you counted 5

So, the missing number is 5! Emma added 5 bits of wood.

## Finding the Unknown Number in Addition – Guided Practice

Let's try another problem together.

Problem

John started with 8 screws and finished with 11. How many screws did he add?

So, the missing number is 3! John added 3 screws.

## Finding the Unknown Number in Addition – Application

Now, try solving this problem on your own:

Problem If Sarah has a pile of 10 seeds and ends with a pile of 16 seeds, how many seeds did she add?

So, the missing number is 6! Sarah added 6 seeds.

### Finding the Unknown Number in Addition – Examples

To be truly fluent in finding the unknown number in addition, have a look at some more examples and complete them by following the steps.

Problem Equation Count Up Solution
9 + ? = 15 9 + ? = 15 10, 11, 12, 13, 14, 15 6
6 + ? = 13 6 + ? = 13 7, 8, 9, 10, 11, 12, 13 7
4 + ? = 10 4 + ? = 10 5, 6, 7, 8, 9, 10 6
3 + ? = 8 3 + ? = 8 4, 5, 6, 7, 8 5

## Finding the Unknown Number in Addition – Summary

Key Learnings from this Text:

• Finding the unknown number in addition helps us solve addition problems by using parts and the whole.
• Write an equation with the parts you know.
• Count up from the known part to the whole to find the missing number.

Keep practising finding the unknown number in addition to become a maths whiz! Check out more fun maths problems and activities on our website.

## Finding the Unknown Number in Addition – Frequently Asked Questions

What is finding the unknown number in addition?
How do you use this method?
Why is it helpful to find the unknown number?
Can you give an example?
What should you remember when finding the unknown number?
What is the "whole" in an addition problem?
How do you write an equation for finding the unknown number?
What do you do after writing the equation?
Is this method only used in addition?
Where can I practise more problems like this?

## Finding the Unknown Number (in Addition) — Let's Practice! exercise

Would you like to apply the knowledge you’ve learnt? You can review and practice it with the tasks for the video Finding the Unknown Number (in Addition) — Let's Practice!.
• ### How many toys did Imani buy?

Hints

Remember, an equation looks like this: part + part = whole.

To work out the missing part, think about how many more you need to add to 9 to reach 12.

Look at this example: Imani has 10 sweets. They get more and now they have 14 sweets. How many did they get?

The equation is: the part we know + the part we don't know = the whole we know.

So

10 + ? = 14

Count on from 10 to reach 14. 10, 11, 12, 13, 14. We counted on 4 more, so 10 + 4 = 14.

Solution

Imani started with 9 toys and ended up with 12 in total, so the equation is 9 + ? = 12.

To find the missing part, count on from 9 to 12. 9, 10, 11, 12. We counted on 3 so this is the missing part.

9 + 3 = 12

The equation 3 + 9 = 12 would also have been correct.

• ### Which numbers are missing?

Hints

Remember, to find the part we don't know, we count up from the part we do know until we reach the whole.

Look at this example: 7 + ? = 14.

We start at the part we know (7) and count up to the whole (14).

7, 8, 9, 10, 11, 12, 13, 14. We counted on 7, so the missing part is 7.

7 + 7 = 14

Solution

7 + 3 = 10 (7, 8, 9, 10)

3 + 6 = 9 (3, 4, 5, 6, 7, 8, 9)

8 + 7 = 15 (8, 9, 10, 11, 12, 13, 14, 15)

• ### What is the missing part?

Hints

Count up from the part you know until you reach the whole.

Look at this example: 8 + ? = 14.

We start at 8, and count up until we reach 14.

8, 9, 10, 11, 12, 13, 14. The missing part is 6.

8 + 6 = 14

Solution

5 + 6 = 11

3 + 7 = 10

9 + 4 = 13

To find the missing numbers, we started at the part we knew and counted up until we reached the whole.

• ### How many flowers did Imani plant?

Hints

Remember, to create an equation, use the numbers you know. We know Mr. Squeaks planted 8 flowers. What else do we know?

Look at the story. What is the whole? How many flowers did they plant together?

An equation looks like this: part + part = whole

To find the missing part, start at the part we know and count up to reach the whole.

Solution

Imani planted 5 flowers.

The equation is: 8 + 5 = 13.

We count up from one part (8) to the whole (13) to find the missing part.

8, 9, 10, 11, 12, 13. The missing number is 5.

• ### How many more nails did Mr. Squeaks find?

Hints

Mr. Squeaks started with 5 nails and finished with 10. Count up from 5 to 10 to find the missing part.

5, 6, 7, 8, 9, 10. How many numbers did we count up?

Solution

Mr. Squeaks found 5 nails in the box.

Count on from 5 to 10: 5, 6, 7, 8, 9, 10. We counted 5 numbers, so 5 is the missing part.

5 + 5 = 10.

• ### The vegetable patch.

Hints

Start with the tomato plants.

Remember, to create an equation, use the numbers you know. We know Imani planted 4 tomatoes. What else do we know?

Look at the story. What is the whole? How many tomatoes did they plant together?

An equation looks like this: part + part = whole

To find the missing part, start at the part we know (4) and count up to reach the whole (13).

Repeat these steps for the bean plants.

Solution

Tomato plants

• 4 + ? = 13
• The missing part is 9.
• Count on from 4 to 13. 4, 5, 6, 7, 8, 9, 10, 11, 12, 13. We counted 9 numbers, so 9 is the missing part.
• 4 + 9 = 13
Bean plants
• 7 + ? = 11
• The missing part is 4.
• Count on from 7 to 11. 7, 8, 9, 10, 11. We counted on 4 numbers, so 4 is the missing part.
• 7 + 4 = 11