Add & Subtract Within 1000 — Answer Key
Part A: Sort the Words
Sort each word or number into the correct category box.
1. Sort each problem by whether regrouping is NEEDED.
No regrouping
123+456305+402710+280444+333 Needs regrouping
248+137562+329 Spotting regroup problems early helps you slow down in the right spots and avoid careless mistakes when adding within 1000.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. 123+456=579
3+6=9, 2+5=7, 1+4=5, so 123+456=579.
2. 305+402=707
5+2=7, 0+0=0, 3+4=7, so the sum is 707.
3. 710+280=990
0+0=0, 1+8=9, 7+2=9, so 710+280=990.
4. 444+333=777
4+3=7 in every column, so the sum is 777.
5. 612+175=787
2+5=7, 1+7=8, 6+1=7, so 612+175=787.
Part C: True or False?
Read each statement. Circle True or False.
1. 123+456=579.
True False
3+6=9, 2+5=7, 1+4=5, so the sum is 579.
2. 305+402=807.
True False
3+4=7 in the hundreds, not 8, so the correct sum is 707, not 807.
3. When you add two 3-digit numbers and no column is more than 9, you do not regroup.
True False
Regrouping starts when a column reaches 10, so if every column stays under 10, no regrouping is needed.
4. 710+280=980.
True False
1+8=9 tens, not 8, so the correct sum is 990, not 980.