Cardinal Math

Two-digit subtraction with regrouping · sheet 30 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 61 − 58 3 13 borrows, but never pays17 smaller from larger
2 65 − 15 50 no pattern to catch here
3 58 − 49 9 11 smaller from larger19 borrows, but never pays
4 84 − 77 7 13 smaller from larger17 borrows, but never pays
5 60 − 44 16 24 smaller from larger26 borrows, but never pays
6 97 − 58 39 41 smaller from larger49 borrows, but never pays
7 65 − 39 26 34 smaller from larger36 borrows, but never pays
8 98 − 80 18 no pattern to catch here
9 77 − 29 48 52 smaller from larger58 borrows, but never pays
10 80 − 66 14 24 borrows, but never pays26 smaller from larger
11 80 − 38 42 52 borrows, but never pays58 smaller from larger
12 43 − 25 18 22 smaller from larger28 borrows, but never pays
13 40 − 22 18 22 smaller from larger28 borrows, but never pays
14 72 − 22 50 no pattern to catch here
15 71 − 39 32 42 borrows, but never pays48 smaller from larger
16 73 − 67 6 14 smaller from larger16 borrows, but never pays
17 12 − 11 1 no pattern to catch here
18 28 − 27 1 no pattern to catch here
19 95 − 69 26 34 smaller from larger36 borrows, but never pays
20 70 − 13 57 63 smaller from larger67 borrows, but never pays

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.