Cardinal Math

Three-digit subtraction with regrouping · sheet 14 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 203 − 172 31 101 zero minus a number is zero131 borrows, but never pays171 smaller from larger or zero minus a number is the number
2 463 − 170 293 313 smaller from larger393 borrows, but never pays
3 540 − 172 368 370 zero minus a number is zero372 zero minus a number is the number432 smaller from larger478 borrows, but never pays
4 345 − 264 81 121 smaller from larger181 borrows, but never pays
5 764 − 169 595 605 borrows, but never pays or smaller from larger
6 929 − 828 101 no pattern to catch here
7 559 − 365 194 214 smaller from larger294 borrows, but never pays
8 322 − 185 137 247 borrows, but never pays263 smaller from larger
9 560 − 299 261 270 zero minus a number is zero279 zero minus a number is the number339 smaller from larger371 borrows, but never pays
10 497 − 479 18 22 smaller from larger28 borrows, but never pays
11 271 − 193 78 122 smaller from larger188 borrows, but never pays
12 858 − 616 242 no pattern to catch here
13 204 − 160 44 104 zero minus a number is zero144 borrows, but never pays164 smaller from larger or zero minus a number is the number
14 501 − 453 48 148 borrowing through a zero152 smaller from larger158 borrows, but never pays
15 603 − 514 89 111 smaller from larger189 borrowing through a zero199 borrows, but never pays
16 285 − 247 38 42 smaller from larger48 borrows, but never pays
17 508 − 229 279 321 smaller from larger379 borrowing through a zero389 borrows, but never pays
18 604 − 393 211 301 zero minus a number is zero311 borrows, but never pays391 smaller from larger or zero minus a number is the number
19 161 − 112 49 51 smaller from larger59 borrows, but never pays
20 608 − 449 159 241 smaller from larger259 borrowing through a zero269 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 5 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 5 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.