Cardinal Math

Two-digit subtraction with regrouping · sheet 5 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 73 − 66 7 13 smaller from larger17 borrows, but never pays
2 90 − 36 54 64 borrows, but never pays66 smaller from larger
3 67 − 39 28 32 smaller from larger38 borrows, but never pays
4 43 − 35 8 12 smaller from larger18 borrows, but never pays
5 90 − 88 2 12 borrows, but never pays18 smaller from larger
6 97 − 89 8 12 smaller from larger18 borrows, but never pays
7 98 − 89 9 11 smaller from larger19 borrows, but never pays
8 97 − 79 18 22 smaller from larger28 borrows, but never pays
9 88 − 77 11 no pattern to catch here
10 96 − 73 23 no pattern to catch here
11 79 − 69 10 no pattern to catch here
12 18 − 12 6 no pattern to catch here
13 24 − 22 2 no pattern to catch here
14 86 − 68 18 22 smaller from larger28 borrows, but never pays
15 30 − 21 9 11 smaller from larger19 borrows, but never pays
16 22 − 13 9 11 smaller from larger19 borrows, but never pays
17 71 − 58 13 23 borrows, but never pays27 smaller from larger
18 56 − 37 19 21 smaller from larger29 borrows, but never pays
19 80 − 61 19 21 smaller from larger29 borrows, but never pays
20 90 − 86 4 14 borrows, but never pays16 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.