Cardinal Math

Two-digit subtraction with regrouping · sheet 7 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 98 − 19 79 81 smaller from larger89 borrows, but never pays
2 76 − 69 7 13 smaller from larger17 borrows, but never pays
3 80 − 16 64 74 borrows, but never pays76 smaller from larger
4 90 − 71 19 21 smaller from larger29 borrows, but never pays
5 30 − 11 19 21 smaller from larger29 borrows, but never pays
6 98 − 87 11 no pattern to catch here
7 97 − 89 8 12 smaller from larger18 borrows, but never pays
8 54 − 26 28 32 smaller from larger38 borrows, but never pays
9 73 − 55 18 22 smaller from larger28 borrows, but never pays
10 46 − 10 36 no pattern to catch here
11 70 − 47 23 33 borrows, but never pays37 smaller from larger
12 93 − 89 4 14 borrows, but never pays16 smaller from larger
13 61 − 27 34 44 borrows, but never pays46 smaller from larger
14 79 − 70 9 no pattern to catch here
15 90 − 67 23 33 borrows, but never pays37 smaller from larger
16 46 − 45 1 no pattern to catch here
17 79 − 49 30 no pattern to catch here
18 96 − 68 28 32 smaller from larger38 borrows, but never pays
19 87 − 78 9 11 smaller from larger19 borrows, but never pays
20 45 − 36 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.