2nd Grade Math Lesson

The Place Value Portal: Mental Jumps of 10 and 100

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2nd GradeBuilding Thinking ClassroomsCCSS.MATH.CONTENT.2.NBT.B.850 min

Learning Objective

Students will mentally add and subtract 10 and 100 to/from any three-digit number up to 1,000, correctly identifying which place-value digit changes while all others remain constant, including across regrouping boundaries.

Lesson Overview

Students use random vertical whiteboard groups to discover that adding or subtracting 10 shifts only the tens digit and adding or subtracting 100 shifts only the hundreds digit — all other digits remain invariant. Tasks progress from single-step jumps on familiar numbers to multi-step chains that cross century boundaries.

Materials

Vertical whiteboards or large chart paper taped to walls
Dry-erase markers (1 per group)
Erasers or socks
Random group generator (e.g., card draw)
Sticky notes for exit slip
Optional: printed 1,000-chart or open number line strips

Scaffolded Task Progression

1Task 1

You are at address

245

. You dial +10 on your portal pad. What is your new address? Write the starting number, the jump, and the landing number on your whiteboard. Circle the digit that changed.

2Task 2

You are at address

372

. You dial −10 on your portal pad. What is your new address? Write it and circle the digit that changed.

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