How it works: a quick refresher
The rules this worksheet practices, then one problem worked from start to finish.
| Strategy | How it works |
|---|---|
| Estimate first | 24 + 38 is about 20 + 40 = 60, so look for a number near 60. |
| Add tens, then ones | 24 + 38: 20 + 30 = 50, 4 + 8 = 12, 50 + 12 = 62. |
| Check the ones digit | 4 + 8 ends in 2, so the total must end in 2. |
| The answer is never the biggest | Every group has a number bigger than the answer. |
Worked example
Find the number made from two others: 24, 38, 51, 62 and 87.
- 1Estimate 24 + 38: about 20 + 40 = 60.
- 2Add exactly: 20 + 30 = 50 and 4 + 8 = 12, so 62.
- 362 is in the group. Circle it and write 24 + 38 = 62.
Ready-made versions
Three fixed versions you can link to or share. Each is a PDF with its own answer key.
- Challenge: six numbers Worksheets, version 1Worksheet PDFAnswer key PDF
- Challenge: six numbers Worksheets, version 2Worksheet PDFAnswer key PDF
- Challenge: six numbers Worksheets, version 3Worksheet PDFAnswer key PDF
Grade level and standard
Written for 2nd grade math (puzzles) and aligned to CCSS 2.NBT.B.5. It also works as review in later grades.
Common questions
- Is there an answer key?
- Yes. Every worksheet has a matching answer key with each answer worked on the same grid or layout as the question. The worksheet code printed at the bottom of each page pairs a sheet with its key.
- My child adds every pair on paper. Is that OK?
- To start, yes. Estimating first saves time: a pair whose total is nowhere near any number in the group can be skipped.
- Is there a version to play on screen?
- Yes. Flip's Number Hunt has the same puzzles as a free game: endlessworksheets.com/games/number-hunt/sums-to-100.
- How many different versions are there?
- About a million per skill. Each time you press the button the problems are generated fresh, so you can print a different version for every student, a retake, or another night of practice.
- Are the worksheets free?
- Yes. They are free to print and copy for your home or classroom, with no sign-up.
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