Cardinal Math

Three-digit subtraction with regrouping · sheet 11 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 205 − 155 50 100 zero minus a number is zero150 borrows, but never pays or smaller from larger or zero minus a number is the number
2 326 − 119 207 213 smaller from larger217 borrows, but never pays
3 249 − 192 57 157 borrows, but never pays or smaller from larger
4 982 − 728 254 264 borrows, but never pays266 smaller from larger
5 547 − 488 59 141 smaller from larger169 borrows, but never pays
6 307 − 143 164 204 zero minus a number is zero244 smaller from larger or zero minus a number is the number264 borrows, but never pays
7 271 − 198 73 127 smaller from larger183 borrows, but never pays
8 317 − 292 25 125 borrows, but never pays185 smaller from larger
9 208 − 159 49 149 borrowing through a zero151 smaller from larger159 borrows, but never pays
10 949 − 745 204 no pattern to catch here
11 624 − 167 457 543 smaller from larger567 borrows, but never pays
12 903 − 219 684 716 smaller from larger784 borrowing through a zero794 borrows, but never pays
13 502 − 472 30 100 zero minus a number is zero130 borrows, but never pays170 smaller from larger or zero minus a number is the number
14 628 − 354 274 334 smaller from larger374 borrows, but never pays
15 961 − 334 627 633 smaller from larger637 borrows, but never pays
16 230 − 174 56 144 smaller from larger166 borrows, but never pays60 zero minus a number is zero64 zero minus a number is the number
17 810 − 294 516 520 zero minus a number is zero524 zero minus a number is the number626 borrows, but never pays684 smaller from larger
18 908 − 639 269 331 smaller from larger369 borrowing through a zero379 borrows, but never pays
19 798 − 526 272 no pattern to catch here
20 904 − 578 326 426 borrowing through a zero436 borrows, but never pays474 smaller from larger

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.