Build from known sums to tens-and-ones addition, then check every answer on the optional key.
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Addition within 100 Worksheet
Solve the addition problems. Write each answer in the space provided.
Name: Date:
Hint: Work with tens and ones; check any crossing-ten step.
Question 1:1.4 + 5 =
Question 2:2.5 + 13 =
Question 3:3.2 + 10 =
Question 4:4.2 + 7 =
Question 5:5.5 + 14 =
Question 6:6.3 + 11 =
Question 7:7.92 + 1 =
Question 8:8.71 + 12 =
Question 9:9.44 + 25 =
Question 10:10.96 + 2 =
Question 11:11.2 + 92 =
Question 12:12.38 + 61 =
Question 13:13.59 + 7 =
Question 14:14.29 + 5 =
Question 15:15.2 + 79 =
Question 16:16.91 + 9 =
Question 17:17.26 + 34 =
Question 18:18.15 + 48 =
Question 19:19.52 + 5 =
Question 20:20.37 + 22 =
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Answer key
Compare each answer with the same question on the worksheet.
1.4 + 5 =9
2.5 + 13 =18
3.2 + 10 =12
4.2 + 7 =9
5.5 + 14 =19
6.3 + 11 =14
7.92 + 1 =93
8.71 + 12 =83
9.44 + 25 =69
10.96 + 2 =98
11.2 + 92 =94
12.38 + 61 =99
13.59 + 7 =66
14.29 + 5 =34
15.2 + 79 =81
16.91 + 9 =100
17.26 + 34 =60
18.15 + 48 =63
19.52 + 5 =57
20.37 + 22 =59
Work with tens and ones
The opening questions recall smaller sums. The middle questions ask you to combine two-digit numbers without crossing ten, then the next group crosses ten. Two mixed questions finish the sheet. Each question has one answer line and the optional key repeats the same numbering.
A useful way to add
For 34 + 25, add the tens (30 + 20 = 50) and the ones (4 + 5 = 9), then combine them to get 59. When the ones total ten or more, regroup that extra ten: 38 + 27 has 8 + 7 = 15, so 30 + 20 + 15 = 65.
