2nd grade mental math worksheets

Mental math worksheets for 2nd grade practice adding and subtracting two-digit numbers in your head with friendly-number strategies: add 30 instead of 29, then adjust. The problems sit horizontally on purpose: there's no column setup, just thinking.

Free printable PDF worksheet, aligned to Common Core 2.OA.B.2, 2.NBT.B.5.

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The kind of problems you'll get

Solve in your head. Write only the answer.

  1. 81 + 29 =

    Answer: 110

  2. ___ + 6 = 20
  3. 76 − 39 =

Every print pulls a fresh set of problems at this level, so a make-up test or a second sibling never gets the same sheet.

What's on each sheet

Every version prints on US Letter or A4, with its answer key on the last page.

How to teach this

Ask "what's the friendly number nearby?" before your child computes. 29 wants to be 30, 41 wants to be 40. Have them say the strategy out loud: "add 30, take 1 back." Keep the pencil away from the working; the answer line is the only writing.

Watch for: Kids set up column arithmetic on paper. This page is head math, so talk through a friendly-number shortcut instead. Kids adjust the wrong way after rounding. If you added 1 to turn 29 into 30, take 1 back off the answer.

Common questions about mental math

Why are the problems written across instead of stacked?
Stacked problems invite column arithmetic, and this page practices thinking, not writing. Horizontal problems nudge your child toward friendly-number strategies.
What strategies should a 2nd grader use?
Adding near-tens (treat 29 as 30, then take 1 back), making a ten, and subtracting a round number then adjusting. Any route that happens in the head counts.

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Aligned to Common Core 2.OA.B.2, 2.NBT.B.5. Reviewed by the One more sheet curriculum team. Content version 123, updated July 2026.