Cardinal Math

Three-digit subtraction with regrouping · sheet 16 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 763 − 287 476 524 smaller from larger586 borrows, but never pays
2 702 − 412 290 300 zero minus a number is zero310 smaller from larger or zero minus a number is the number390 borrows, but never pays
3 354 − 296 58 142 smaller from larger168 borrows, but never pays
4 290 − 227 63 70 zero minus a number is zero73 borrows, but never pays77 smaller from larger or zero minus a number is the number
5 404 − 287 117 217 borrowing through a zero227 borrows, but never pays283 smaller from larger
6 821 − 640 181 221 smaller from larger281 borrows, but never pays
7 920 − 591 329 330 zero minus a number is zero331 zero minus a number is the number439 borrows, but never pays471 smaller from larger
8 632 − 361 271 331 smaller from larger371 borrows, but never pays
9 560 − 172 388 390 zero minus a number is zero392 zero minus a number is the number412 smaller from larger498 borrows, but never pays
10 208 − 138 70 100 zero minus a number is zero130 smaller from larger or zero minus a number is the number170 borrows, but never pays
11 503 − 495 8 108 borrowing through a zero118 borrows, but never pays192 smaller from larger
12 903 − 235 668 732 smaller from larger768 borrowing through a zero778 borrows, but never pays
13 974 − 168 806 814 smaller from larger816 borrows, but never pays
14 682 − 572 110 no pattern to catch here
15 430 − 214 216 220 zero minus a number is zero224 smaller from larger or zero minus a number is the number226 borrows, but never pays
16 268 − 179 89 111 smaller from larger199 borrows, but never pays
17 448 − 285 163 243 smaller from larger263 borrows, but never pays
18 656 − 455 201 no pattern to catch here
19 603 − 556 47 147 borrowing through a zero153 smaller from larger157 borrows, but never pays
20 901 − 491 410 500 zero minus a number is zero510 borrows, but never pays590 smaller from larger or zero minus a number is the number

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.