Finding the Unknown Number (in Addition) — Let's Practice!
 Finding the Unknown Number in Addition – Introduction
 What Is Finding the Unknown Number in Addition?
 Finding the Unknown Number in Addition – Example
 Finding the Unknown Number in Addition – Guided Practice
 Finding the Unknown Number in Addition – Application
 Finding the Unknown Number in Addition – Summary
 Finding the Unknown Number in Addition – Frequently Asked Questions
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

Show the correct equation.
HintsRemember, an equation looks like this: part + part = whole
Look at this example. Imani has 10 candies. He gets more, and now he has 14 candies. How many did he get?
The equation is: the part we know + the part we don't know = the whole we know.
10 + ? = 14
SolutionThe equation we would write is 4 + ? = 13. We know Imani had 4 toys. Then, they added more and end with 13. The whole is 13, and one part is 4: 4 + ? = 13.
To solve, Imani counts up from 4 (5, 6, 7, 8, 9, 10, 11, 12, 13) to find that they added 9 toys from the store.
4 + 9 = 13

Select the appropriate numbers to complete the equations.
HintsRemember, 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. The missing part is 7.
Solution7 + 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)

Fill in the missing part.
HintsCount 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
Solution5 + 6 = 11
3 + 7 = 10
9 + 4 = 13
To find the missing numbers, we started at the part and counted up until we reached the whole.

Create the equation and solve.
HintsRemember, 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.
SolutionImani planted 5 flowers.
The equation is: 8 + 5 = 13.
We count up from one part (8) to the whole (13) to solve for the missing part.
8, 9, 10, 11, 12, 13. The missing number is 5.

Count up to find the missing part.
HintsMr. Squeaks started with 6 toys and finished with 10. Count up from 6 to find the missing part.
Part + part = whole
SolutionImani gave Mr. Squeaks 4 toys today!
Mr. Squeaks already had 6 toys, and Imani gave him more. Now he has 10 toys. The equation is: 6 + ? = 10.
To solve, start at 6, and count up until 10. 6, 7, 8, 9, 10. The missing part is 4.

Finish the equation and solve.
HintsRemember, 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).
SolutionMr. Squeaks planted 9 tomato plants!
The equation is: 4 + 9 = 13.
We count up from one part (4) to the whole (13) to find the missing part.
4, 5, 6, 7, 8, 9, 10, 11, 12, 13. The missing number is 9*