Cardinal Math

Two-digit subtraction with regrouping · sheet 9 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 95 − 76 19 21 smaller from larger29 borrows, but never pays
2 46 − 27 19 21 smaller from larger29 borrows, but never pays
3 87 − 34 53 no pattern to catch here
4 97 − 38 59 61 smaller from larger69 borrows, but never pays
5 90 − 81 9 11 smaller from larger19 borrows, but never pays
6 88 − 23 65 no pattern to catch here
7 35 − 34 1 no pattern to catch here
8 97 − 89 8 12 smaller from larger18 borrows, but never pays
9 75 − 29 46 54 smaller from larger56 borrows, but never pays
10 78 − 49 29 31 smaller from larger39 borrows, but never pays
11 72 − 71 1 no pattern to catch here
12 85 − 25 60 no pattern to catch here
13 75 − 66 9 11 smaller from larger19 borrows, but never pays
14 30 − 11 19 21 smaller from larger29 borrows, but never pays
15 74 − 16 58 62 smaller from larger68 borrows, but never pays
16 51 − 39 12 22 borrows, but never pays28 smaller from larger
17 90 − 88 2 12 borrows, but never pays18 smaller from larger
18 50 − 18 32 42 borrows, but never pays48 smaller from larger
19 82 − 25 57 63 smaller from larger67 borrows, but never pays
20 70 − 59 11 21 borrows, but never pays29 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.