# Interesting Number Facts for Elementary and Middle School Students How can you get your students engaged and excited about mathematics? Maybe you’ve seen some fun math facts for kids that can pique students’ curiosity. Those statements and brain-teasers can be a great way to challenge students, help them think critically, and enable them to develop an appreciation for the beauty of mathematics. On a wider scale, all those things are powerful for enhancing their interest and comfort with STEM subjects.

The following sections offer some interesting number facts that you can present to students to showcase mathematical concepts. ## 5 Interesting Number Facts

### 1.    There are 86,400 seconds in a day.

A day can seem short. However, when you convert it to a much smaller unit of time, the result can seem much larger than expected. Surprise your younger students with this fact to help them put time into perspective. Older students can work on word problems and calculating how much time something takes.

#### Tips for Implementing the Fact

• Consider starting the lesson by telling students how many seconds there are in a minute or day, depending on the grade level, or you can ask them to estimate or calculate the answer.
• Turn it into an interactive activity and think about how to illustrate time with fun games for your students. One lesson plan from Education World recommends having students place their heads on their desks. After you say “go” and start a stopwatch, they quietly raise their hands when they think 60 seconds has expired.
• Have students convert other units of time. For instance, they can determine how many minutes are in a day.

#### Related Facts

• There are more than 31 million seconds in a year. (To be precise, there are 31,536,000 seconds.)

### 2.    The only prime numbers that end with a “2” or “5” are two and five.

There is an infinite amount of prime numbers — as ancient Greek mathematician Euclid, as well as several modern mathematics have proven — but only two and five end with the digits “2” and “5.” That fact makes it an excellent segue into the world of prime numbers.

#### Tips for Implementing the Fact

• Provide students with the definition of a prime number (a whole number greater than 1 whose factors are only 1 and itself) and some examples of prime numbers, such as 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29. Have them explain why 5 and 7 are prime numbers but 8 and 9 aren’t prime numbers.
• Have students find prime numbers from a range, such as 80-100.
• For older students, discuss why it’s so difficult to factor large numbers into their prime factors. You can then introduce why prime numbers are used by information technology experts to encrypt data.

#### Related Facts

• The only even prime number is two. That’s because all other even numbers can be divided by two, which eliminates numbers from being prime numbers.
• The largest known prime number has 23,249,425 digits. It’s referred to as M77232917, and it was discovered in January 2018 by a computer in Tennessee. ### 3.    In a room of 23 people, there’s a 50 percent chance of two people having the same birthday.

Some of the most fun math facts for kids are great for introducing them to certain concepts. If you’re looking for a segue to probability, the “birthday problem” or “birthday paradox” could be your best bet.

Graphic/helpful but not required: Can we recreate this? We shouldn’t need any attribution, given how popular this problem is.

#### Tips for Implementing the Fact

• One key to understanding the birthday paradox is that, in a group of 23 people, there are 253 combinations of birthdays that can be made. That’s more than half the number of days in a year (183).
• Ask your students to test the theory. They can produce random dates online and see how many times it takes to get a match. Another option is to survey people at school. Discuss the results and come up with the minimum, maximum, and average number of times it took to find duplicate birthdays.
• You can always introduce probability with the birthday problem but have the lesson focus on something simpler. In that case, help students determine the chance of flipping a coin and getting heads three times in a row. They can then perform experiments to see how the results relate to probability.

#### Related Facts

• It only takes 70 people for the probability of two people having the same birthday to reach 99.9 percent. At 367 people, it’s 100 percent probable.
• An interesting bit of trivia is that the most common birthday in the United States currently is September 9, according to Time magazine. ### 4.    Π is an irrational number discovered more than a thousand years ago.

Ancient civilizations knew the value of π to two decimal places, and by the fifth century, Chinese mathematicians approximated the number to seven digits. Introducing your students to π or “pi” can help them better understand something central to geometry and other mathematical fields. There are plenty of interesting number facts for one of the most special and exciting numbers.

#### Tips for Implementing the Fact

• Explain why π is an irrational number. There are no fractions equivalent to it, and its decimal representation never ends.
• Showcase the formulas involving π, including the circumference and area of a circle. Have students work on some simple calculations to see how effective π is in geometry.

#### Related Facts

• The world record holder for memorizing digits of π belongs to Lu Chao of China, who recited 67,890 digits in 2005, according to Live Science.
• “Pi” day is celebrated on March 14 (3/14). Looking for an exact match for π’s first 10 digits? It only comes once a century, according to NBC News, and the most recent moment was in 2015. The next opportunity is in 2115, when 3/14/15, 9:26:53 will be the magic moment.

### 5.    The angles of a triangle always add up to 180 degrees.

There are several types of triangles, but the sum of all angles will always be 180 degrees. This interesting number fact can help you introduce the basics of triangles.

#### Tips for Implementing the Fact

• Have students look at the different types of triangles. There are equilateral, isosceles, scalene, obtuse, acute, and right-angle triangles. How do they differ? How are they alike?
• Give students practice calculating the missing angle of a triangle. For instance, what’s the third angle of a triangle with two angles of 120 degrees and 30 degrees?
• Provide real-world relevance to triangles by discussing how they’re used in construction. The first entry in the “related facts” section below offers additional ideas.

#### Related Facts

• Triangles are the strongest shape, as Underground Mathematics explains, comparing triangles to other polygons.

• The ancient Greek mathematician Pythagoras determined that for a right triangle, the square of the longest side (hypotenuse) is equal to the squares of the other two sides. That’s represented in the equation known as “Pythagoras’ Theorem,” or a2 + b2 = c2.

## Encourage Your Students in Mathematics and Other STEM Subjects

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