Find the error: 2-digit addition with regrouping

A find-the-error worksheet for two-digit sums where the ones make a new ten, like 48 + 37. Each problem shows a student's worked solution with one planted mistake; students find the wrong step, name the misconception and solve it correctly. The answer key is computed, so it is always right.

Make this worksheet "Is it right?" version

Mistakes this sheet plants

Forgot to regroup. 6 + 6 = 12 makes a new ten, but the 1 ten was never added to the tens.Example: 46 + 26 worked to 62 instead of 72.
Wrote the whole ones sum. The ones make 11. Only the 1 goes in the ones place; the 1 ten is regrouped, not written next to it.Example: 24 + 37 worked to 511 instead of 61.

Grade 2 · 2.NBT.B.5

Find the error: 2-digit addition with regrouping

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 24 + 37

Leo's work

24+37511
1. Add the ones: 4 + 7 = 11. Write 11.
2. Add the tens: 2 + 3 = 5.
Leo's answer: 511

Wrong step: What went wrong: Correct answer:
2 46 + 26

Maya's work

46+2662
1. Add the ones: 6 + 6 = 12. Write 2.
2. Add the tens: 4 + 2 = 6.
Maya's answer: 62

Wrong step: What went wrong: Correct answer:
3 69 + 16

Ava's work

69+1675
1. Add the ones: 9 + 6 = 15. Write 5.
2. Add the tens: 6 + 1 = 7.
Ava's answer: 75

Wrong step: What went wrong: Correct answer:
4 68 + 19

Kai's work

68+19717
1. Add the ones: 8 + 9 = 17. Write 17.
2. Add the tens: 6 + 1 = 7.
Kai's answer: 717

Wrong step: What went wrong: Correct answer:

Free sheet from stepcheck.apps.clod.farm · every answer computed, not generated · sheet sample-two-digit-addition-regrouping

Answer key · Grade 2 · 2.NBT.B.5

Find the error: 2-digit addition with regrouping

#	Wrong step	The mistake	Correct answer
1	Step 1	Wrote the whole ones sum. The ones make 11. Only the 1 goes in the ones place; the 1 ten is regrouped, not written next to it.Correct step 1: Add the ones: 4 + 7 = 11. Write 1, regroup 1 to the tens.	61not 511
2	Step 1	Forgot to regroup. 6 + 6 = 12 makes a new ten, but the 1 ten was never added to the tens.Correct step 1: Add the ones: 6 + 6 = 12. Write 2, regroup 1 to the tens.	72not 62
3	Step 1	Forgot to regroup. 9 + 6 = 15 makes a new ten, but the 1 ten was never added to the tens.Correct step 1: Add the ones: 9 + 6 = 15. Write 5, regroup 1 to the tens.	85not 75
4	Step 1	Wrote the whole ones sum. The ones make 17. Only the 7 goes in the ones place; the 1 ten is regrouped, not written next to it.Correct step 1: Add the ones: 8 + 9 = 17. Write 7, regroup 1 to the tens.	87not 717

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