Second Grade · Math · week 18

Checkpoint: regrouping with blocks

Demonstrate and explain addition and subtraction regrouping using base-ten blocks.

This checkpoint is about explaining, not just answering. Use blocks to show a friend or family member exactly what happens when you regroup while adding or subtracting.

A strong explanation names the trade: "10 ones become 1 ten" when adding, or "1 ten becomes 10 ones" when subtracting.

📋 For the teacher
Teach it (10–15 min):
  • Ask them to teach YOU the steps using the blocks, as if you do not already know how -- teaching back is the best test of real understanding.
  • Require the specific trade language, "10 ones for 1 ten" or "1 ten for 10 ones" -- a vague explanation means it is not solid yet.
  • Mix one addition and one subtraction regrouping problem so both directions get checked.
  • If the explanation stumbles, go back to slow, hands-on regrouping practice before moving on to money and time.
Talk about it:
  • Can you show me, with blocks, exactly where the extra ten comes from when you add?
  • Can you show me, with blocks, exactly what happens when you unbundle a ten to subtract?
  • Which direction of regrouping, adding or subtracting, feels more solid to you right now?

Mastery looks like: They demonstrate and explain both addition and subtraction regrouping with blocks, using accurate trade language.

Common stumbles: Getting the right final answer but being unable to explain WHY the trade happened; confusing which direction the trade goes.

See it visually

Interactive, spoken-aloud tools that show this idea in motion.

Place ValueWatch ones, tens, hundreds, and thousands build big numbers.try →SubtractionTake away and count back, step by step.try →AdditionSee groups combine — with counters, blocks, and the number line.try →
Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
Records attendance + 15 min of Math for this learner.
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