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?

Useful methods include breaking numbers into tens and ones, making a ten, and replacing a near-ten with a round number before adjusting. The explanation questions focus on place value and compensation.

2nd grade mental math

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. Some worksheets ask students to choose a place-value or compensation strategy and explain why it works.

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

Each print is a different sheet with its own answer key. You don't need to sign up.

The kind of problems you'll get

Use a friendly ten or hundred, then adjust. Write the missing number. You may jot a step below each problem.

13 + 10 =
Answer: 23
53 + 29 =
Answer: 82
15 + 29 =
Answer: 44

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 a 2nd grade sheet

The sample sheet above has 12 problems. Its answers run from 2 to 82.

Mental math. Use a friendly ten or hundred, then adjust. Write the missing number. You may jot a step below each problem. 12 problems per page.
Mental math strategies. Choose why each strategy works. Complete its equation. 4 problems per page.

Every version prints on US Letter or A4, with its answer key after the problems.

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." When an explanation is requested, have your child connect each adjustment to the original numbers with words or an equation.

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 2nd grade 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?: Useful methods include breaking numbers into tens and ones, making a ten, and replacing a near-ten with a round number before adjusting. The explanation questions focus on place value and compensation.

Related worksheets

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Aligned to Common Core 2.NBT.B.5. Reviewed by the One more sheet team. Content version 241, updated October 2026.

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