Find the original amount
Reconstruct a starting amount from a removed part and remainder.
Explore this lesson →8 practice questions · Optional read aloud · Thinking pad
Let’s understand the idea.
- The starting amount may be unknown even when the story describes removal.
- Use both the removed amount and what remains.
- Choose an equation from the relationship, not a single action word.
Something to notice
Ask the learner to explain why subtracting the two visible numbers would not recreate the original amount.
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.