Cardinal Math

Two-digit subtraction with regrouping · sheet 10 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 79 − 62 17 no pattern to catch here
2 67 − 18 49 51 smaller from larger59 borrows, but never pays
3 93 − 89 4 14 borrows, but never pays16 smaller from larger
4 88 − 79 9 11 smaller from larger19 borrows, but never pays
5 65 − 28 37 43 smaller from larger47 borrows, but never pays
6 95 − 89 6 14 smaller from larger16 borrows, but never pays
7 85 − 74 11 no pattern to catch here
8 90 − 84 6 14 smaller from larger16 borrows, but never pays
9 96 − 75 21 no pattern to catch here
10 90 − 68 22 32 borrows, but never pays38 smaller from larger
11 88 − 69 19 21 smaller from larger29 borrows, but never pays
12 58 − 57 1 no pattern to catch here
13 74 − 35 39 41 smaller from larger49 borrows, but never pays
14 89 − 85 4 no pattern to catch here
15 91 − 82 9 11 smaller from larger19 borrows, but never pays
16 70 − 48 22 32 borrows, but never pays38 smaller from larger
17 65 − 47 18 22 smaller from larger28 borrows, but never pays
18 93 − 57 36 44 smaller from larger46 borrows, but never pays
19 30 − 26 4 14 borrows, but never pays16 smaller from larger
20 80 − 61 19 21 smaller from larger29 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.