Cardinal Math

Two-digit subtraction with regrouping · sheet 11 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 96 − 86 10 no pattern to catch here
2 63 − 37 26 34 smaller from larger36 borrows, but never pays
3 97 − 83 14 no pattern to catch here
4 96 − 91 5 no pattern to catch here
5 60 − 59 1 11 borrows, but never pays19 smaller from larger
6 82 − 49 33 43 borrows, but never pays47 smaller from larger
7 93 − 24 69 71 smaller from larger79 borrows, but never pays
8 90 − 88 2 12 borrows, but never pays18 smaller from larger
9 85 − 69 16 24 smaller from larger26 borrows, but never pays
10 65 − 37 28 32 smaller from larger38 borrows, but never pays
11 17 − 12 5 no pattern to catch here
12 62 − 56 6 14 smaller from larger16 borrows, but never pays
13 86 − 67 19 21 smaller from larger29 borrows, but never pays
14 90 − 18 72 82 borrows, but never pays88 smaller from larger
15 53 − 43 10 no pattern to catch here
16 91 − 88 3 13 borrows, but never pays17 smaller from larger
17 25 − 19 6 14 smaller from larger16 borrows, but never pays
18 60 − 18 42 52 borrows, but never pays58 smaller from larger
19 40 − 38 2 12 borrows, but never pays18 smaller from larger
20 41 − 18 23 33 borrows, but never pays37 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.