Cardinal Math

Two-digit subtraction with regrouping · sheet 22 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 90 − 86 4 14 borrows, but never pays16 smaller from larger
2 42 − 34 8 12 smaller from larger18 borrows, but never pays
3 78 − 32 46 no pattern to catch here
4 68 − 39 29 31 smaller from larger39 borrows, but never pays
5 80 − 13 67 73 smaller from larger77 borrows, but never pays
6 87 − 19 68 72 smaller from larger78 borrows, but never pays
7 58 − 29 29 31 smaller from larger39 borrows, but never pays
8 46 − 45 1 no pattern to catch here
9 20 − 17 3 13 borrows, but never pays17 smaller from larger
10 89 − 69 20 no pattern to catch here
11 59 − 38 21 no pattern to catch here
12 78 − 73 5 no pattern to catch here
13 80 − 34 46 54 smaller from larger56 borrows, but never pays
14 71 − 55 16 24 smaller from larger26 borrows, but never pays
15 96 − 78 18 22 smaller from larger28 borrows, but never pays
16 92 − 15 77 83 smaller from larger87 borrows, but never pays
17 90 − 19 71 81 borrows, but never pays89 smaller from larger
18 92 − 86 6 14 smaller from larger16 borrows, but never pays
19 75 − 26 49 51 smaller from larger59 borrows, but never pays
20 78 − 59 19 21 smaller from larger29 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.