Cardinal Math

Two-digit subtraction with regrouping · sheet 20 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 64 − 54 10 no pattern to catch here
2 50 − 18 32 42 borrows, but never pays48 smaller from larger
3 42 − 39 3 13 borrows, but never pays17 smaller from larger
4 87 − 79 8 12 smaller from larger18 borrows, but never pays
5 90 − 52 38 42 smaller from larger48 borrows, but never pays
6 83 − 47 36 44 smaller from larger46 borrows, but never pays
7 70 − 43 27 33 smaller from larger37 borrows, but never pays
8 78 − 68 10 no pattern to catch here
9 19 − 14 5 no pattern to catch here
10 90 − 59 31 41 borrows, but never pays49 smaller from larger
11 38 − 37 1 no pattern to catch here
12 53 − 17 36 44 smaller from larger46 borrows, but never pays
13 96 − 47 49 51 smaller from larger59 borrows, but never pays
14 44 − 16 28 32 smaller from larger38 borrows, but never pays
15 83 − 35 48 52 smaller from larger58 borrows, but never pays
16 90 − 48 42 52 borrows, but never pays58 smaller from larger
17 95 − 88 7 13 smaller from larger17 borrows, but never pays
18 78 − 30 48 no pattern to catch here
19 35 − 19 16 24 smaller from larger26 borrows, but never pays
20 84 − 68 16 24 smaller from larger26 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.