Work from familiar facts into hundreds, tens and ones, then practise regrouping across a hundred.
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Addition within 1,000 Worksheet
Solve the addition problems. Write each answer in the space provided.
Name: Date:
Hint: Keep hundreds, tens and ones in place; check when you cross a hundred.
Question 1:1.41 + 13 =
Question 2:2.80 + 5 =
Question 3:3.71 + 27 =
Question 4:4.25 + 43 =
Question 5:5.83 + 12 =
Question 6:6.74 + 11 =
Question 7:7.879 + 120 =
Question 8:8.372 + 12 =
Question 9:9.821 + 155 =
Question 10:10.649 + 143 =
Question 11:11.459 + 4 =
Question 12:12.252 + 9 =
Question 13:13.229 + 175 =
Question 14:14.37 + 289 =
Question 15:15.533 + 399 =
Question 16:16.396 + 448 =
Question 17:17.753 + 198 =
Question 18:18.866 + 34 =
Question 19:19.556 + 251 =
Question 20:20.858 + 32 =
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Answer key
Compare each answer with the same question on the worksheet.
1.41 + 13 =54
2.80 + 5 =85
3.71 + 27 =98
4.25 + 43 =68
5.83 + 12 =95
6.74 + 11 =85
7.879 + 120 =999
8.372 + 12 =384
9.821 + 155 =976
10.649 + 143 =792
11.459 + 4 =463
12.252 + 9 =261
13.229 + 175 =404
14.37 + 289 =326
15.533 + 399 =932
16.396 + 448 =844
17.753 + 198 =951
18.866 + 34 =900
19.556 + 251 =807
20.858 + 32 =890
Build up to three-digit sums
The first group warms up with smaller facts. The middle group combines larger numbers without passing a hundred, followed by a group that does pass a hundred. The last two questions are mixed. Write one answer per numbered line; the optional key matches the same questions.
Keep place values aligned
For 243 + 126, combine 200 + 100, 40 + 20, and 3 + 6 to get 369. For 378 + 147, the ones make 15 and the tens make 110, so regroup: 300 + 100 + 110 + 15 = 525. Estimate first to catch an answer that has lost a hundred.
