Cardinal Math

Two-digit subtraction with regrouping · sheet 12 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 99 − 86 13 no pattern to catch here
2 80 − 69 11 21 borrows, but never pays29 smaller from larger
3 67 − 28 39 41 smaller from larger49 borrows, but never pays
4 59 − 29 30 no pattern to catch here
5 80 − 28 52 62 borrows, but never pays68 smaller from larger
6 88 − 79 9 11 smaller from larger19 borrows, but never pays
7 60 − 29 31 41 borrows, but never pays49 smaller from larger
8 82 − 80 2 no pattern to catch here
9 93 − 27 66 74 smaller from larger76 borrows, but never pays
10 77 − 29 48 52 smaller from larger58 borrows, but never pays
11 92 − 89 3 13 borrows, but never pays17 smaller from larger
12 90 − 83 7 13 smaller from larger17 borrows, but never pays
13 39 − 37 2 no pattern to catch here
14 40 − 22 18 22 smaller from larger28 borrows, but never pays
15 86 − 69 17 23 smaller from larger27 borrows, but never pays
16 96 − 19 77 83 smaller from larger87 borrows, but never pays
17 83 − 37 46 54 smaller from larger56 borrows, but never pays
18 72 − 62 10 no pattern to catch here
19 92 − 85 7 13 smaller from larger17 borrows, but never pays
20 31 − 19 12 22 borrows, but never pays28 smaller from larger

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.