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

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Finding the Unknown Number (in Addition) — Let's Practice!
CCSS.MATH.CONTENT.1.OA.A.1

Basics on the topic Finding the Unknown Number (in Addition) — Let's Practice!

Finding the Unknown Number in Addition – Introduction

Get a piece of paper and a pencil ready because today we're going to practice finding the unknown number in addition. It’s a cool trick that helps you figure out missing parts in math 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 practice this with some fun problems!

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 Pictorial representation
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 practicing finding the unknown number in addition to become a math whiz! Check out more fun math problems and activities on our website.

Finding the Unknown Number in Addition – Frequently Asked Questions

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

Razzi says get a piece of paper and pencil ready (...) Because today we're going to practice... Finding the unknown number (in addition). It's time to begin! Remember, you can use parts, whole, and addition to help find the missing number. If Mr. Squeaks started with seven bits of wood for his new project, and ended up with twelve, how many bits did he add? Remember to write an equation, and fill in the parts that you know. Then, count up from part one until you reach the whole. How many numbers did you count? Did you also count five? So, the missing number is five! Let's tackle the next problem! Mr. Squeaks now has started building using screws. If he started with eight screws and finished with eleven, how many screws did he add? Remember to write an equation, and fill in the parts that you know. Then, count up from part one until you reach the whole. How many numbers did you count? Did you also count three ? So, the missing number is three! Let's tackle the next problem! If Mr. Squeaks has a pile of ten seeds and ends with a pile of sixteen seeds, how many seeds did he add? Remember to write an equation, and fill in the parts that you know. Then, count up from part one until you reach the whole. How many numbers did you count? Did you also count six ? The missing number is six! Razzi had so much fun practicing with you today! See you next time!

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

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video Finding the Unknown Number (in Addition) — Let's Practice!.