Cardinal Math

Two-digit subtraction with regrouping · sheet 2 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 86 − 79 7 13 smaller from larger17 borrows, but never pays
2 71 − 31 40 no pattern to catch here
3 79 − 72 7 no pattern to catch here
4 95 − 77 18 22 smaller from larger28 borrows, but never pays
5 82 − 78 4 14 borrows, but never pays16 smaller from larger
6 78 − 69 9 11 smaller from larger19 borrows, but never pays
7 78 − 50 28 no pattern to catch here
8 44 − 40 4 no pattern to catch here
9 60 − 16 44 54 borrows, but never pays56 smaller from larger
10 90 − 67 23 33 borrows, but never pays37 smaller from larger
11 36 − 18 18 22 smaller from larger28 borrows, but never pays
12 60 − 14 46 54 smaller from larger56 borrows, but never pays
13 93 − 76 17 23 smaller from larger27 borrows, but never pays
14 80 − 76 4 14 borrows, but never pays16 smaller from larger
15 62 − 34 28 32 smaller from larger38 borrows, but never pays
16 75 − 58 17 23 smaller from larger27 borrows, but never pays
17 99 − 49 50 no pattern to catch here
18 82 − 73 9 11 smaller from larger19 borrows, but never pays
19 92 − 66 26 34 smaller from larger36 borrows, but never pays
20 60 − 52 8 12 smaller from larger18 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.