Error analysis for grades 2 to 7

Find-the-error math worksheets with answer keys that are always right

stepcheck is a free generator for printable find-the-error worksheets. Each problem shows a student's worked solution with one realistic mistake, like a forgotten regroup or added denominators. The answer key names the wrong step, the misconception and the correct answer.

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18 skills, 41 named misconceptions, Common Core aligned
Fresh numbers every time; each link reprints the same sheet
Every answer computed by code and tested, no AI model writes the problems
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Grade 5 · 5.NF.A.1

Find the error: adding fractions with unlike denominators

Name Date

Each problem was solved by a student, and each has exactly one mistake. Find the step with the mistake, say what went wrong, and solve the problem correctly.

1 38 + 14

Zoe's work
1. Find a common denominator: the least common multiple of 8 and 4 is 8.
2. Rename: 38 = 38 and 14 = 18.
3. Add the numerators: 38 + 18 = 48.
4. Simplify: 48 = 12.
Zoe's answer: 12

Wrong step: What went wrong: Correct answer:
2 38 + 712

Jon's work
1. Add the numerators and the denominators: 3 + 7 = 10 and 8 + 12 = 20, so 1020.
2. Simplify: 1020 = 12.
Jon's answer: 12

Wrong step: What went wrong: Correct answer:

A real sheet from the generator: open it. Its key:

Answer key · Grade 5 · 5.NF.A.1

Adding fractions with unlike denominators

#	Wrong step	The mistake	Correct answer
1	Step 2	Changed the denominator but not the numerator. When the denominator is changed to 8, the numerator must be multiplied by the same number.Correct step 2: Rename: 38 = 38 and 14 = 28.	58not 12
2	Step 1	Added the numerators and the denominators. Denominators name the size of the pieces; they are not added. Rename both fractions with a common denominator (24) first.Correct step 1: Find a common denominator: the least common multiple of 8 and 12 is 24.	2324not 12

How a sheet is made

Nothing on a sheet is typed by hand or written by a language model, so nothing on it can be made up.

You pick a skill, a count and a type. "Find the error" puts one mistake in every problem; "Is it right?" leaves about a third of them correct.
Code picks numbers and solves each problem twice. Once correctly, once the way a student with a specific misconception would, for example adding the denominators.
The first step where the two solutions differ is the wrong step. That step, the misconception and the correct answer go into the key.
Every release is tested. For every skill and every misconception, tests check the right answer and the planted one against separate formulas on hundreds of number sets each.

Skills and the mistakes they plant

Each skill has its own page with a sample sheet. Codes are the Common Core State Standards the skill practices.

Grade	Skill	Mistakes it plants	Standard
2	2-digit addition with regrouping	Forgot to regroup; Wrote the whole ones sum	2.NBT.B.5
2	2-digit subtraction with regrouping	Subtracted the smaller digit from the larger; Regrouped but did not take the ten away	2.NBT.B.5
3	3-digit addition with regrouping	Forgot to regroup; Wrote the whole column sum	3.NBT.A.2
3	Rounding to the nearest 10, 100 or 1,000	Looked at the wrong digit; Rounded 5 down; Cut off the digits instead of rounding	3.NBT.A.1, 4.NBT.A.3
3	Subtraction across zeros	Subtracted the smaller digit from the larger; Left the zero as 10 after regrouping through it	3.NBT.A.2, 4.NBT.B.4
4	2-digit by 2-digit multiplication	Forgot the placeholder zero; Added the carried digit before multiplying; Multiplied only tens by tens and ones by ones	4.NBT.B.5, 5.NBT.B.5
4	Comparing decimals	Thought more digits means a bigger number; Thought tenths always beat hundredths	4.NF.C.7, 5.NBT.A.3b
4	Multiplying a fraction by a whole number	Multiplied the numerator and the denominator; Multiplied the denominator instead of the numerator	4.NF.B.4
5	Adding decimals	Lined up the last digits instead of the decimal points; Forgot to regroup across the decimal point	5.NBT.B.7
5	Adding fractions with unlike denominators	Added the numerators and the denominators; Changed the denominator but not the numerator	5.NF.A.1
5	Long division (zeros in the quotient, remainders)	Left out the zero in the quotient; Wrote the remainder as a decimal	4.NBT.B.6, 5.NBT.B.6
5	Multiplying decimals	Counted the decimal places of only one factor; Multiplied the whole parts and the decimal parts separately	5.NBT.B.7, 6.NS.B.3
6	One-step equations	Used the same operation instead of the inverse; Divided the wrong way round; Subtracted the coefficient instead of dividing	6.EE.B.7
6	Order of operations	Worked left to right, ignoring multiplication first; Added before subtracting; Read the exponent as multiplication	5.OA.A.1, 6.EE.A.2c
6	The distributive property	Multiplied only the first term; Lost the sign when multiplying by a negative	6.EE.A.3, 7.EE.A.1
7	Adding and subtracting integers	Subtracted a negative as if it were positive; Added the sizes when the signs are different; Kept the sign of the first number	7.NS.A.1
7	Multiplying and dividing integers	Said negative times negative is negative; Made the answer positive because there were negatives to cancel	7.NS.A.2
7	Two-step equations	Divided only one side's term; Used the wrong inverse operation on the constant	7.EE.B.4a

Why not an AI worksheet maker?

A chatbot can write a wrong worked solution, but it can also write a wrong answer key, and on a find-the-error sheet you can't tell which mistakes were meant. A key with an unplanned error costs a lesson and some trust.

stepcheck's problems come from small programs, one per skill, that do the arithmetic. The same numbers and the same mistakes come out every time for the same link, and the tests run before every release.

Pricing

Free

Unlimited sheets, all 18 skills
Answer key on its own page
Shareable links
Small stepcheck footer on each sheet

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$4/month or $29/year

Your own sheet title, no footer
Print the answer key on its own
Mixed review sheets across skills

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Questions teachers ask

What is a find-the-error worksheet?

It shows problems that a student has already worked, step by step, with a mistake in the work. Your students find the wrong step, explain the misconception behind it and solve the problem correctly. It is also called error analysis.

Are the answer keys always right?

Yes. No AI model writes the problems. Code picks the numbers, solves each problem correctly, then solves it again with one named misconception, so both the right answer and the planted mistake are computed. Automated tests check every skill and every mistake against separate formulas on thousands of number sets before each release.

Which grades and skills are covered?

Grades 2 to 7: 18 skills from 2-digit addition with regrouping to two-step equations, with 41 named misconceptions in total. The full list with Common Core codes is on the skills page.

Can I print it or save it as a PDF?

Yes. Press Print on the generator page; the sheet prints on US Letter with the answer key on its own page. To get a PDF, choose Save as PDF in the print dialog.

Do I get the same sheet again?

Every sheet has a link with its seed. The same link always prints the same numbers, so you can share it with a colleague or reprint it next year. New numbers gives a fresh sheet.

Do students need accounts?

No. stepcheck is for teachers, tutors and parents. There are no student accounts, and we collect no student data.

Is it free?

Yes: unlimited sheets with a small footer. Pro ($4/month or $29/year) will add custom titles, no footer, answer key only and mixed review sheets. Pro isn't open yet.

Last updated 2026-10-02.