What could the original have been?
Find every possible whole-number original behind a rounded report.
Explore this lesson →7 practice questions · Optional read aloud · Thinking pad
Let’s understand the idea.
- A rounded report can stand for many exact original amounts.
- The lower halfway value rounds into the reported multiple. The next upper halfway value rounds into the next multiple.
- For whole numbers, the last included value is one less than that next halfway value.
- Include both ends of the range and keep originals between zero and one million. Nearest-one rounding has only one possible original.
Something to notice
Ask the learner to test both endpoints and one value just outside each allowed endpoint. Have them explain why the lower tie is included and the upper tie is excluded. Discuss why a report of zero can still represent a positive exact count.
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.NBT · 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.