Cardinal Math

Two-digit subtraction with regrouping · sheet 15 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 40 − 34 6 14 smaller from larger16 borrows, but never pays
2 93 − 90 3 no pattern to catch here
3 53 − 39 14 24 borrows, but never pays26 smaller from larger
4 90 − 81 9 11 smaller from larger19 borrows, but never pays
5 30 − 29 1 11 borrows, but never pays19 smaller from larger
6 97 − 89 8 12 smaller from larger18 borrows, but never pays
7 89 − 78 11 no pattern to catch here
8 93 − 56 37 43 smaller from larger47 borrows, but never pays
9 80 − 77 3 13 borrows, but never pays17 smaller from larger
10 49 − 18 31 no pattern to catch here
11 50 − 20 30 no pattern to catch here
12 90 − 57 33 43 borrows, but never pays47 smaller from larger
13 67 − 48 19 21 smaller from larger29 borrows, but never pays
14 84 − 78 6 14 smaller from larger16 borrows, but never pays
15 95 − 66 29 31 smaller from larger39 borrows, but never pays
16 86 − 79 7 13 smaller from larger17 borrows, but never pays
17 68 − 65 3 no pattern to catch here
18 93 − 84 9 11 smaller from larger19 borrows, but never pays
19 86 − 17 69 71 smaller from larger79 borrows, but never pays
20 43 − 27 16 24 smaller from larger26 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.