Find the error: 2-digit subtraction with regrouping

A find-the-error worksheet for two-digit differences that need a ten broken into ones, like 52 − 27. 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.

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Mistakes this sheet plants

Subtracted the smaller digit from the larger. In the ones, 2 is less than 7. Instead of regrouping, the student did 7 − 2.Example: 72 − 37 worked to 45 instead of 35.
Regrouped but did not take the ten away. The ones became 15, but the tens digit should then go from 7 to 6.Example: 75 − 59 worked to 26 instead of 16.

Grade 2 · 2.NBT.B.5

Find the error: 2-digit subtraction 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 72 − 37

Jon's work

72−3745
1. Ones: 7 − 2 = 5.
2. Tens: 7 − 3 = 4.
Jon's answer: 45

Wrong step: What went wrong: Correct answer:
2 75 − 59

Mia's work

75−5926
1. Ones: 5 is less than 9, so make it 15.
2. Ones: 15 − 9 = 6.
3. Tens: 7 − 5 = 2.
Mia's answer: 26

Wrong step: What went wrong: Correct answer:
3 53 − 18

Eli's work

53−1845
1. Ones: 3 is less than 8, so make it 13.
2. Ones: 13 − 8 = 5.
3. Tens: 5 − 1 = 4.
Eli's answer: 45

Wrong step: What went wrong: Correct answer:
4 82 − 57

Maya's work

82−5735
1. Ones: 7 − 2 = 5.
2. Tens: 8 − 5 = 3.
Maya's answer: 35

Wrong step: What went wrong: Correct answer:

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

Answer key · Grade 2 · 2.NBT.B.5

Find the error: 2-digit subtraction with regrouping

#	Wrong step	The mistake	Correct answer
1	Step 1	Subtracted the smaller digit from the larger. In the ones, 2 is less than 7. Instead of regrouping, the student did 7 − 2.Correct step 1: Ones: 2 is less than 7. Regroup 1 from the tens: 7 becomes 6, and the ones become 12.	35not 45
2	Step 1	Regrouped but did not take the ten away. The ones became 15, but the tens digit should then go from 7 to 6.Correct step 1: Ones: 5 is less than 9. Regroup 1 from the tens: 7 becomes 6, and the ones become 15.	16not 26
3	Step 1	Regrouped but did not take the ten away. The ones became 13, but the tens digit should then go from 5 to 4.Correct step 1: Ones: 3 is less than 8. Regroup 1 from the tens: 5 becomes 4, and the ones become 13.	35not 45
4	Step 1	Subtracted the smaller digit from the larger. In the ones, 2 is less than 7. Instead of regrouping, the student did 7 − 2.Correct step 1: Ones: 2 is less than 7. Regroup 1 from the tens: 8 becomes 7, and the ones become 12.	25not 35

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