A number in every place
Find the unknown in addition and subtraction equations.
Explore this lesson →8 practice questions · Optional read aloud · Thinking pad
Let’s understand the idea.
- The missing number can appear at the start, in the middle, or at the end.
- Find the number that makes both sides equal. The position of the equal sign does not change its meaning.
- Put your number into the original equation and check both sides.
Try it. Change it. Explain it.
Open the lesson to use its pictures and controls. In How it works, connect the picture to the idea. In Play & discover, change the quantities and notice what stays the same. In Your turn, answer questions and use the explanation to check your reasoning.
You can ask for help, draw on the thinking pad, or listen to the question and answer options. Progress distinguishes independent work from work completed with help.
Let’s try it →Curriculum connection
Grade 1 · 1.OA · US Common Core
This lesson is mapped to these standards. A completed activity is practice evidence, not a claim of mastery. Content is checked against the linked official standards and its mathematical models are tested.