Cardinal Math

Two-digit subtraction with regrouping · sheet 1 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 82 − 69 13 23 borrows, but never pays27 smaller from larger
2 95 − 49 46 54 smaller from larger56 borrows, but never pays
3 70 − 63 7 13 smaller from larger17 borrows, but never pays
4 51 − 45 6 14 smaller from larger16 borrows, but never pays
5 60 − 33 27 33 smaller from larger37 borrows, but never pays
6 70 − 51 19 21 smaller from larger29 borrows, but never pays
7 33 − 24 9 11 smaller from larger19 borrows, but never pays
8 40 − 33 7 13 smaller from larger17 borrows, but never pays
9 82 − 14 68 72 smaller from larger78 borrows, but never pays
10 93 − 74 19 21 smaller from larger29 borrows, but never pays
11 49 − 29 20 no pattern to catch here
12 93 − 89 4 14 borrows, but never pays16 smaller from larger
13 53 − 45 8 12 smaller from larger18 borrows, but never pays
14 99 − 87 12 no pattern to catch here
15 99 − 89 10 no pattern to catch here
16 61 − 15 46 54 smaller from larger56 borrows, but never pays
17 80 − 72 8 12 smaller from larger18 borrows, but never pays
18 87 − 79 8 12 smaller from larger18 borrows, but never pays
19 33 − 31 2 no pattern to catch here
20 89 − 84 5 no pattern to catch here

Reading the wrong answers

One wrong answer is a slip. The same pattern on three or more problems is a rule your child is following, and it has a name and a fix in the guide. Problems marked "no pattern to catch" are the plain ones; a child who gets only those right is telling you something too.

Borrows, but never pays 15 of 20 problems

Adds ten to the ones but leaves the tens alone. Looks like borrowing; the answer is ten too big.

52 − 38 they write 24 it is 14

Smaller from larger 15 of 20 problems

Takes the smaller digit from the bigger one in every column, whichever is on top. Never borrows.

52 − 38 they write 26 it is 14

Not sure which? The five-minute check picks the problems that tell the patterns apart and names the one it sees.