Thinking Summary · 1
Mastered[object Object]
[Discovery] Place 91 on the number line between 90 and 100.
1
Active Step[Discovery] Place 91 on the number line between 90 and 100.
Number Line
Place the marker on 91.
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90 ⟵ ⟶ 100
Welcome to "Probe Round-Up", a Grade 3 Rounding to the Nearest Ten or Hundred mission at the Explorer core practice level, staged in a space scenario. The mission opens with a hands-on prompt: "Place 91 on the number line between 90 and 100." Students work with the numbers 91, 90, 100 and reach a final answer of 100 across 3 guided steps.
Behind the story, this lesson builds rounding to the nearest ten or hundred understanding aligned to CCSS 3.NBT.A.1. The key strategy is: Halfway rule: if the gap ≥ 5, round UP.
A common misconception this page surfaces is: Always rounding down (chopping the ones digit). Check both sides: which ten is closer? 38 is closer to 40, not 30. The adaptive Socratic hints move from a small nudge to a fuller strategy, keeping the reasoning visible for students, parents, and teachers.
Grade 3 · Rounding to the Nearest Ten or Hundred
Mission Progress
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Thinking Summary · 1
Mastered[object Object]
[Discovery] Place 91 on the number line between 90 and 100.
1
Active StepPlace the marker on 91.
Everything you need to know about the Socratic experience.
Place 91 on the number line between 90 and 100. Hint: 91 sits between 90 and 100. Find its exact tick.
What is the next multiple of 10 ABOVE 91? If you get stuck, the adaptive hint is: 90 + 10 = ?
Explorer missions hit the core abstraction at typical numeric ranges — this is where conceptual mastery is built. Within Grade 3 Rounding to the Nearest Ten or Hundred, expect numbers in the corresponding range.
Always rounding down (chopping the ones digit). Check both sides: which ten is closer? 38 is closer to 40, not 30.
Multi-digit Addition (Rounding lets students sanity-check large sums by estimation.) Open /grade-3/addition to start that topic's missions.
Inquiry-based learning starts with a question, not a formula — students explore, hypothesize, and verify before being told the rule. In Inquiry AI, every mission opens with a "Discovery" step (manipulate the model), then "Abstraction" (write the equation), then "Reflect" (apply to a new case). The procedure is never given upfront; learners derive it from their own observations.
Yes. Every mission, handbook page, and topic hub is mapped to a specific CCSS code (visible in the page header). The curriculum follows the CCSS coherence map: Grade 1 number sense → Grade 3 multiplicative thinking → Grade 6 ratio reasoning, with each grade building strictly on the prior year's foundations.