Cardinal Math

Three-digit subtraction with regrouping · sheet 18 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 308 − 209 99 101 smaller from larger109 borrows, but never pays199 borrowing through a zero
2 468 − 277 191 211 smaller from larger291 borrows, but never pays
3 192 − 113 79 81 smaller from larger89 borrows, but never pays
4 800 − 743 57 100 zero minus a number is zero143 smaller from larger or zero minus a number is the number157 borrowing through a zero167 borrows, but never pays
5 928 − 579 349 451 smaller from larger459 borrows, but never pays
6 202 − 136 66 134 smaller from larger166 borrowing through a zero176 borrows, but never pays
7 602 − 351 251 301 zero minus a number is zero351 borrows, but never pays or smaller from larger or zero minus a number is the number
8 567 − 176 391 411 smaller from larger491 borrows, but never pays
9 309 − 189 120 200 zero minus a number is zero220 borrows, but never pays280 smaller from larger or zero minus a number is the number
10 623 − 109 514 524 borrows, but never pays526 smaller from larger
11 307 − 259 48 148 borrowing through a zero152 smaller from larger158 borrows, but never pays
12 968 − 857 111 no pattern to catch here
13 344 − 125 219 221 smaller from larger229 borrows, but never pays
14 925 − 760 165 245 smaller from larger265 borrows, but never pays
15 923 − 256 667 733 smaller from larger777 borrows, but never pays
16 870 − 287 583 590 zero minus a number is zero597 zero minus a number is the number617 smaller from larger693 borrows, but never pays
17 760 − 191 569 570 zero minus a number is zero571 zero minus a number is the number631 smaller from larger679 borrows, but never pays
18 917 − 779 138 208 zero minus a number is zero248 borrows, but never pays262 smaller from larger278 zero minus a number is the number
19 878 − 545 333 no pattern to catch here
20 301 − 241 60 100 zero minus a number is zero140 smaller from larger or zero minus a number is the number160 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.