Cardinal Math

Two-digit subtraction with regrouping · sheet 13 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 60 − 39 21 31 borrows, but never pays39 smaller from larger
2 70 − 52 18 22 smaller from larger28 borrows, but never pays
3 40 − 19 21 31 borrows, but never pays39 smaller from larger
4 84 − 66 18 22 smaller from larger28 borrows, but never pays
5 88 − 39 49 51 smaller from larger59 borrows, but never pays
6 64 − 56 8 12 smaller from larger18 borrows, but never pays
7 50 − 33 17 23 smaller from larger27 borrows, but never pays
8 92 − 58 34 44 borrows, but never pays46 smaller from larger
9 98 − 52 46 no pattern to catch here
10 81 − 49 32 42 borrows, but never pays48 smaller from larger
11 85 − 39 46 54 smaller from larger56 borrows, but never pays
12 44 − 34 10 no pattern to catch here
13 28 − 12 16 no pattern to catch here
14 86 − 17 69 71 smaller from larger79 borrows, but never pays
15 73 − 67 6 14 smaller from larger16 borrows, but never pays
16 63 − 57 6 14 smaller from larger16 borrows, but never pays
17 19 − 17 2 no pattern to catch here
18 70 − 14 56 64 smaller from larger66 borrows, but never pays
19 94 − 27 67 73 smaller from larger77 borrows, but never pays
20 68 − 67 1 no pattern to catch here

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.