Cardinal Math

Two-digit subtraction with regrouping · sheet 21 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 92 − 84 8 12 smaller from larger18 borrows, but never pays
2 98 − 49 49 51 smaller from larger59 borrows, but never pays
3 75 − 19 56 64 smaller from larger66 borrows, but never pays
4 27 − 22 5 no pattern to catch here
5 70 − 37 33 43 borrows, but never pays47 smaller from larger
6 95 − 39 56 64 smaller from larger66 borrows, but never pays
7 82 − 79 3 13 borrows, but never pays17 smaller from larger
8 66 − 61 5 no pattern to catch here
9 65 − 18 47 53 smaller from larger57 borrows, but never pays
10 56 − 43 13 no pattern to catch here
11 90 − 86 4 14 borrows, but never pays16 smaller from larger
12 90 − 89 1 11 borrows, but never pays19 smaller from larger
13 90 − 48 42 52 borrows, but never pays58 smaller from larger
14 94 − 56 38 42 smaller from larger48 borrows, but never pays
15 79 − 56 23 no pattern to catch here
16 66 − 49 17 23 smaller from larger27 borrows, but never pays
17 65 − 46 19 21 smaller from larger29 borrows, but never pays
18 75 − 47 28 32 smaller from larger38 borrows, but never pays
19 75 − 55 20 no pattern to catch here
20 80 − 71 9 11 smaller from larger19 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.