Cardinal Math

Three-digit subtraction with regrouping · sheet 24 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 231 − 162 69 131 smaller from larger179 borrows, but never pays
2 941 − 344 597 603 smaller from larger607 borrows, but never pays
3 308 − 120 188 208 zero minus a number is zero228 smaller from larger or zero minus a number is the number288 borrows, but never pays
4 461 − 180 281 321 smaller from larger381 borrows, but never pays
5 779 − 244 535 no pattern to catch here
6 350 − 194 156 160 zero minus a number is zero164 zero minus a number is the number244 smaller from larger266 borrows, but never pays
7 404 − 176 228 328 borrowing through a zero338 borrows, but never pays372 smaller from larger
8 376 − 262 114 no pattern to catch here
9 204 − 107 97 103 smaller from larger107 borrows, but never pays197 borrowing through a zero
10 801 − 340 461 501 zero minus a number is zero541 smaller from larger or zero minus a number is the number561 borrows, but never pays
11 278 − 269 9 11 smaller from larger19 borrows, but never pays
12 954 − 679 275 325 smaller from larger385 borrows, but never pays
13 720 − 412 308 310 zero minus a number is zero312 smaller from larger or zero minus a number is the number318 borrows, but never pays
14 279 − 184 95 115 smaller from larger195 borrows, but never pays
15 200 − 108 92 100 zero minus a number is zero102 borrows, but never pays108 smaller from larger or zero minus a number is the number192 borrowing through a zero
16 403 − 260 143 203 zero minus a number is zero243 borrows, but never pays263 smaller from larger or zero minus a number is the number
17 307 − 268 39 139 borrowing through a zero149 borrows, but never pays161 smaller from larger
18 425 − 360 65 145 smaller from larger165 borrows, but never pays
19 167 − 128 39 41 smaller from larger49 borrows, but never pays
20 680 − 195 485 490 zero minus a number is zero495 zero minus a number is the number515 smaller from larger595 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 18 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 18 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

Zero minus a number is the number 7 of 20 problems

When the top digit is 0, writes the bottom digit as that column's answer.

40 − 27 they write 27 it is 13

Zero minus a number is zero 7 of 20 problems

When the top digit is 0, writes 0 for that column.

40 − 27 they write 20 it is 13

Borrowing through a zero 4 of 20 problems

Turns the 0 into a 9 and gives the ones their ten, but never reduces the column left of the zero.

302 − 167 they write 235 it is 135

Not sure which? The five-minute check picks the problems that tell the patterns apart and names the one it sees.