Cardinal Math

Two-digit subtraction with regrouping · sheet 29 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 93 − 86 7 13 smaller from larger17 borrows, but never pays
2 45 − 38 7 13 smaller from larger17 borrows, but never pays
3 98 − 36 62 no pattern to catch here
4 90 − 43 47 53 smaller from larger57 borrows, but never pays
5 92 − 28 64 74 borrows, but never pays76 smaller from larger
6 95 − 18 77 83 smaller from larger87 borrows, but never pays
7 85 − 46 39 41 smaller from larger49 borrows, but never pays
8 91 − 72 19 21 smaller from larger29 borrows, but never pays
9 77 − 40 37 no pattern to catch here
10 87 − 39 48 52 smaller from larger58 borrows, but never pays
11 80 − 71 9 11 smaller from larger19 borrows, but never pays
12 90 − 63 27 33 smaller from larger37 borrows, but never pays
13 50 − 32 18 22 smaller from larger28 borrows, but never pays
14 71 − 49 22 32 borrows, but never pays38 smaller from larger
15 18 − 17 1 no pattern to catch here
16 90 − 88 2 12 borrows, but never pays18 smaller from larger
17 32 − 15 17 23 smaller from larger27 borrows, but never pays
18 87 − 65 22 no pattern to catch here
19 67 − 66 1 no pattern to catch here
20 46 − 28 18 22 smaller from larger28 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.