Cardinal Math

Three-digit subtraction with regrouping · sheet 19 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 829 − 433 396 416 smaller from larger496 borrows, but never pays
2 639 − 217 422 no pattern to catch here
3 773 − 637 136 144 smaller from larger146 borrows, but never pays
4 234 − 226 8 12 smaller from larger18 borrows, but never pays
5 605 − 232 373 403 zero minus a number is zero433 smaller from larger or zero minus a number is the number473 borrows, but never pays
6 559 − 235 324 no pattern to catch here
7 284 − 128 156 164 smaller from larger166 borrows, but never pays
8 501 − 253 248 348 borrowing through a zero352 smaller from larger358 borrows, but never pays
9 973 − 691 282 322 smaller from larger382 borrows, but never pays
10 604 − 548 56 144 smaller from larger156 borrowing through a zero166 borrows, but never pays
11 905 − 468 437 537 borrowing through a zero547 borrows, but never pays563 smaller from larger
12 580 − 292 288 290 zero minus a number is zero292 zero minus a number is the number312 smaller from larger398 borrows, but never pays
13 423 − 196 227 337 borrows, but never pays373 smaller from larger
14 750 − 382 368 370 zero minus a number is zero372 zero minus a number is the number432 smaller from larger478 borrows, but never pays
15 207 − 189 18 118 borrowing through a zero128 borrows, but never pays182 smaller from larger
16 704 − 684 20 100 zero minus a number is zero120 borrows, but never pays180 smaller from larger or zero minus a number is the number
17 402 − 110 292 302 zero minus a number is zero312 smaller from larger or zero minus a number is the number392 borrows, but never pays
18 937 − 550 387 427 smaller from larger487 borrows, but never pays
19 658 − 459 199 201 smaller from larger209 borrows, but never pays
20 617 − 249 368 408 zero minus a number is zero432 smaller from larger448 zero minus a number is the number478 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 6 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 6 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.