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Adding and Subtracting Within 100

A 45-minute Grade 2 lesson on fluent two-digit addition and subtraction, where regrouping is taught as a trade between columns rather than as a digit that jumps.

Adding and Subtracting Within 100 is a free 45-minute Grade 2 maths lesson plan for Common Core standard 2.NBT.B.5 — add and subtract within 100 confidently. It is timed across 5 sections, gives the exact wording to use where the wording carries the mathematics, names 3 misconceptions with the teaching move that addresses each, and ends with an exit ticket and a printable worksheet with its answer key.

Grade:
Grade 2
Length:
45 minutes
Standard:
2.NBT.B.5

Grade 2 · Number & Operations in Base Ten

2.NBT.B.5

Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.

Objective

Students will be able to add and subtract two-digit numbers within 100, regrouping between tens and ones when needed.

Students are successful when they can

  • Adds two two-digit numbers with and without regrouping.
  • Subtracts with regrouping, explaining what was traded.
  • Checks a subtraction by adding the answer back.

What you need

  • Base ten rods and units
  • Place value mats
  • A number line for the counting-on strategy
  • The printable practice sheet linked at the end of this plan

The lesson

Warm-up — no regrouping first

5 min
  1. Give four calculations with no regrouping needed: 34 + 25, 67 − 42, and two more.
  2. Ask how they knew no trade was needed. Looking at the ones before starting is the habit being built.

Teach — trading, both directions

13 min
  1. Build 47 + 28 on a place value mat. Add the ones: fifteen units, too many for the column.
  2. Trade ten units for one rod. Seven rods, five units: 75. Write the calculation alongside the materials.
  3. Now 62 − 35. Try to take five units from two. There are not enough.
  4. Trade one rod for ten units, so 62 becomes five rods and twelve units. Nothing was added or removed — it was exchanged.
  5. Now take away three rods and five units: 27.
  6. Check by adding 27 + 35 back. Getting 62 is the confirmation, and doing it here builds the habit.
“You are not moving a digit. You are swapping ten of one thing for one of another. The number does not change when you trade it.”

Guided practice — predict the trade

12 min
  1. Pairs sort a set of calculation cards into 'needs a trade' and 'does not' before solving any.
  2. They then solve them with materials, checking their sort was right.
  3. Every subtraction gets checked by adding back.

Independent practice

12 min
  1. Students complete a mixed addition and subtraction page.
  2. The classic error is subtracting the smaller ones digit from the larger regardless of which is on top. Look for it specifically.

Close

3 min
  1. Give 52 − 27 and ask what has to be traded before any answer is offered.
  2. Naming the trade in advance is what stops the smaller-from-larger error.

What goes wrong, and why

Each of these is a reasoning error rather than carelessness. The fix addresses the reasoning.

Answers 62 − 35 as 33 by doing 5 − 2 in the ones column.

Why: Subtraction is being performed digit by digit with the smaller taken from the larger, because that is the only subtraction the pupil can do without a trade and the column has to produce something.

Fix: Build it. Two units genuinely cannot give five away, and the impossibility is visible before the trade is offered as the solution.

Writes 47 + 28 as 615 — fifteen in the ones and six in the tens.

Why: Each column has been added correctly and written down as it came, with no rule preventing a two-digit entry in a one-digit column.

Fix: Use the place value mat with a physical limit of nine per column. The overflow forces the trade rather than the rule being recited.

Regroups when it is not needed.

Why: Regrouping has been learned as part of the procedure rather than as a response to a specific situation.

Fix: Sort calculations into needs-a-trade and does-not before solving. Deciding is a separate step and doing it explicitly stops it being automatic.

If they are not there yet

  • Work without regrouping for a full session, then addition with regrouping, then subtraction. Three separate skills learned in order beat one confusing session.
  • Keep the base ten materials out. The written method is a record of the trade, and pupils who lose the materials early lose the meaning.

If they finish early

  • Add three two-digit numbers.
  • Subtract by counting on from the smaller number and compare the effort with the written method for 71 − 68.
  • Find the missing number in 43 + ___ = 81.

Exit ticket

Work out 53 − 28. Then check your answer by adding.

What to look for: 25, with 25 + 28 = 53 as the check. An answer of 35 is the smaller-from-larger error and the check would have caught it — insist on the check.

Printable practice for 2.NBT.B.5

Free to print and copy, answer key included. Each sheet can generate a fresh set of problems for a retake.

Questions about Adding and Subtracting Within 100

How long does the Adding and Subtracting Within 100 lesson take?

45 minutes, split across 5 timed sections: warm-up 5 min, teach 13 min, guided practice 12 min, independent practice 12 min, close 3 min. The minutes are stated per section and add up to the stated length, so the plan can be cut or extended at a section boundary rather than abandoned halfway.

Which standard does Adding and Subtracting Within 100 teach?

CCSS.MATH.CONTENT.2.NBT.B.5 — 2.NBT.B.5, Number & Operations in Base Ten for Grade 2: “Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.” In plain terms, add and subtract within 100 confidently.

What do I need to teach this lesson?

Base ten rods and units, place value mats, a number line for the counting-on strategy and the printable practice sheet linked at the end of this plan. Everything listed is either ordinary classroom equipment or a free printable from this site — there is nothing to buy and nothing to prepare beyond photocopying.

What mistakes should I expect in this lesson?

Three, each a reasoning error rather than carelessness: answers 62 − 35 as 33 by doing 5 − 2 in the ones column; writes 47 + 28 as 615 — fifteen in the ones and six in the tens and regroups when it is not needed. The plan gives the thinking behind each one and the teaching move that addresses the thinking rather than the symptom.

How do I know whether the lesson worked?

The exit ticket asks: “Work out 53 − 28. Then check your answer by adding.” 25, with 25 + 28 = 53 as the check. An answer of 35 is the smaller-from-larger error and the check would have caught it — insist on the check. That tells you whether the class needs a reteach or a thirty-second conversation before you plan tomorrow.

Is there a worksheet to go with Adding and Subtracting Within 100?

Yes — 2 printable 2.NBT.B.5 worksheets, linked at the end of the plan and free like the rest of the site. Each one comes with an answer key and 25 versions, so the practice after the lesson can be a different paper on every desk.

Is Adding and Subtracting Within 100 free to use?

Yes. The plan, its printables and their answer keys are free to read, print and photocopy for your own class, with no account and no email capture. It was last reviewed on 5 September 2026. Please do not resell it or republish it as your own.

Last reviewed 2026-09-05. Aligned to 2.NBT.B.5 of the Common Core State Standards for mathematics.