For many teachers, early February marks the 100th day of school. It is certainly a milestone worth celebrating!
Historically, the reason why 100 seems so important is because humans typically have 10 fingers, and 10 times 10 is 100. This anatomical accident has made the number 100 important, both in and out of the math classroom. It’s a “round” number, and in many contexts, it’s the first “big” round number.
Download 100th day of school math activities for students
What better way to celebrate than with some puzzles featuring the number 100? The puzzles below give students a fun way to practice operations with whole numbers through 100. They rely on recognizing ways to make multiples of 10 (for example, spotting that 27 and 23 add to 50) and discovering strategies to make 100 (for example, rewriting an expression as 25 × 4).
The puzzles are appropriate for students in second grade and older. The challenge puzzles, which require knowledge of fractions and division, are better suited for students in fifth grade and older. In particular, the puzzles practice these standards:
- Fluently add and subtract within 100 (Grade 2)
- Perform operations with whole numbers and decimals through 100 (Grade 5)
These 100th day of school math activities will stretch the brains of students of all ages, including adults!
Fun facts about the number 100
Once students have completed the 100th day of school math printable activities, you can share these fun facts with them about the number 100.
- We have 100 US senators because there are 50 states and two senators per state.
- 100 is the basis for the idea of a percent. Percent comes from per centum, or per hundred, in Latin.
- Also coming from the Latin word centum is C, is the Roman numeral for 100.
- On Rosh Hashanah, the Jewish New Year, many rabbis blow the shofar (an ancient musical instrument made from a ram’s horn) 100 times.
- 100 has the unusual property that it can be written as ab+ ba. Can you figure out a and b? (See the end of this post for the solution.)
- The number 100 has a few unusual connections to prime numbers. The sum of the first nine prime numbers is 100. Also, there are exactly 100 prime numbers whose digits are in strictly ascending order (for example, 349 counts because it’s prime and 3 < 4 < 9).
- In the US, we dial the phone number 9-1-1 when we need immediate help. However, in Greece, India, Israel, and Nepal, people dial 1-0-0 for police, and in Belgium, people dial 1-0-0 for an ambulance or firefighter.
- On March 2, 1962, Wilt Chamberlain set a record for the highest number of points scored in one NBA game by a single player—100.
- There are 100 tiles in a standard English Scrabble set. Want to quickly check if your Scrabble set has all the tiles? Tournament players group them into four sets of 5 × 5 tiles along the four corners of the playing board. That way before beginning a game, both players can easily see that there are 4 × 25, or 100, tiles.
Solution: 26 + 62 = 100.
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This blog, originally published in 2020, has been updated for 2025.
Did you enjoy our 100th day math activities? Learn more about HMH's comprehensive math solutions for students in Grades Pre-K–12.
For more ways to celebrate the 100th day of school with your students, check out these articles:
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