← Back to Addition to 20

Addition to 20 - Worksheet 8 - 1st Grade

Hard

Add with sums up to 20 (Hard)

30 problems · 10-15 minutes · Skills: addition, mental math

About This Worksheet

This hard-level worksheet contains 30 problems designed for 1st Grade students practicing addition to 20. Hard worksheets feature challenging problems including multi-step questions, missing values, and real-world applications to push students further.

Addition to 20 introduces regrouping concepts and the powerful "make a ten" strategy that students will use throughout their math education.

How to Solve: Worked Example

Example Problem: 8 + ___ = 15
Solution Steps:
  1. Think: 8 + ? = 15.
  2. Count up from 8 to 15: 9, 10, 11, 12, 13, 14, 15 — that's 7 jumps.
  3. Or: 15 − 8 = 7.
Answer: 7
Tip: You can also use subtraction to solve missing addend problems: total − known part = missing part.
1
12 + ___ = 18
2
Start at 10, jump 10 on the number line = ___
3
8 + 5 =
4
Start at 8, jump 11 on the number line = ___
5
11 + 6 =
6
Start at 7, jump 8 on the number line = ___
7
Start at 13, jump 4 on the number line = ___
8
4 + ___ = 13
9
11 + 5 =
10
13 + ___ = 18
11
13 + ___ = 19
12
Start at 13, jump 4 on the number line = ___
13
Start at 7, jump 4 on the number line = ___
14
16 + ___ = 19
15
10 + ___ = 19
16
5 + 6 =
17
Start at 10, jump 8 on the number line = ___
18
9 + 8 =
19
9 + ___ = 17
20
6 + 9 =
21
7 + ___ = 20
22
12 + ___ = 18
23
6 + 8 =
24
Start at 9, jump 10 on the number line = ___
25
Start at 8, jump 8 on the number line = ___
26
Start at 10, jump 6 on the number line = ___
27
17 + ___ = 20
28
13 + ___ = 19
29
Start at 14, jump 6 on the number line = ___
30
Start at 14, jump 5 on the number line = ___

Answer Key

1. 62. 203. 134. 195. 176. 157. 178. 99. 1610. 511. 612. 1713. 1114. 315. 916. 1117. 1818. 1719. 820. 1521. 1322. 623. 1424. 1925. 1626. 1627. 328. 629. 2030. 19

Frequently Asked Questions

How do I download this addition to 20 - worksheet 8 worksheet?

Click the "Download PDF / Print" button at the top of the worksheet. You can save it as a PDF or print it directly. The answer key will be on a separate page.

How do I find worksheets at different difficulty levels?

Each subtopic has 10 worksheets: Worksheets 1-3 are Easy, 4-7 are Medium, and 8-10 are Hard. Start with Easy worksheets to build confidence, then progress to harder ones.

How many problems are on this worksheet?

This worksheet contains 30 problems. It typically takes 10-15 minutes to complete. An answer key with all solutions is included.