Check by going back
Use related addition or subtraction equations to justify a mixed result.
Explore this lesson →8 practice questions · Optional read aloud · Thinking pad
Let’s understand the idea.
- A subtraction can be checked by adding the removed and remaining amounts.
- An addition can be checked by removing one addend from the total.
- The related equation uses the same three quantities and compatible units.
Something to notice
Invite the learner to point from each quantity in the original calculation to its role in the related equation.
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 4 · 4.NF · 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.