Finding the Unknown Number (in Addition)

Rating

Ø 5.0 / 2 ratings

The authors
Team Digital
Finding the Unknown Number (in Addition)
CCSS.MATH.CONTENT.1.OA.A.1

Basics on the topicFinding the Unknown Number (in Addition)

Two Digit Addition with Missing Numbers

In this video, Mr. Squeaks and Imani are getting ready for hibernation. In order to do so, they need to gather many nuts and seeds to keep themselves warm and full all winter long! However as they gather, they notice that their piles are growing. They know how much they started with, and how many they have now, but how much was added? They can use missing number addition! Read more below to learn about 1st grade addition missing number.

Usually, we add one part plus another part to find the whole. We also sometimes call the parts addends, and the whole, sum. But, what happens when you don't know one of the parts? How can you find the missing number in addition? When you don’t know one of the parts, it is missing. How can we find missing addends?

How to Find the Missing Number in Addition

Even if we are missing some parts and don’t know them, we can STILL use the parts, the whole, and addition to help us. In order to find the missing number…

• Start by setting up the addition equation using the plus sign
• Next, write in the numbers you know and put a question mark for the one you don't.
• Then, count up from part one until you reach the whole. The amount of numbers we counted is the missing part!

Let’s practice missing numbers in equations with the example below.

Mr. Squeaks has found one of his favorite snacks, carrots! He started with seven carrots and found some more. If he has sixteen carrots now, how many more carrots did he find? We can use missing number addition to help!

• Start by setting up the addition equation using the plus sign
• Next, write in the numbers you know and put a question mark for the one you don't.
• Then, count up from part one until you reach the whole. The amount of numbers we counted is the missing part!

Finding the Unknown Number (in Addition) - Summary

Today we learned how to find the missing number in addition. This can be helpful when you know some parts and a whole but are missing some information in an addition equation. When looking for a missing number in addition…

• Start by setting up an addition equation
• Next, write in the numbers you know and put a question mark for the one you don't.
• Then, count up from part one until you reach the whole. That’s the missing number!