Fascinating Maths Facts
1. If you write out pi to two decimal places, backwards it spells “pie”.
4. 111,111,111 × 111,111,111 = 12,345,678,987,654,321.
It also works for smaller numbers: 111 × 111 = 12321.
5. In a room of just 23 people there’s a 50% chance that two people have the same birthday.
It’s called the Birthday Problem. In a room of 75 there’s a 99% chance of two people matching.
6. Zero is the only number that can’t be represented in Roman numerals.
The Latin word “nulla” would have been used instead.
7. Zero is an even number.
But people take longer to decide whether it’s even or odd because it’s not as easy for us to mentally categorise.
8. The most popular favourite number is 7.
Nearly 3000 people, around 10% of the total asked, chose 7 as their favourite number in an online poll by Alex Bellos. The second most popular was 3.
9. .999999… = 1
Here’s the proof:
If 10N = 9.9999…
Then N = .9999….
Subtract N from 10N, leaving you with 9N=9.
So then N=1. But we already know that N=.9999… as well.
So 1=.9999….
Then N = .9999….
Subtract N from 10N, leaving you with 9N=9.
So then N=1. But we already know that N=.9999… as well.
So 1=.9999….
10. 10! seconds is exactly 6 weeks.
10! means 10 factorial. 10! = 10 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1 = 3628800 seconds. Which is 42 days, or 6 weeks, exactly.
11. Take any four digit number, follow these steps, and you’ll end up with 6174.
1. Choose a four digit number (the only condition is that it has at least two different digits).
2. Arrange the digits of the four digit number in descending then ascending order.
3. Subtract the smaller number from the bigger one.
4. Repeat.
2. Arrange the digits of the four digit number in descending then ascending order.
3. Subtract the smaller number from the bigger one.
4. Repeat.
Eventually you’ll end up at 6174, which is known as Kaprekar’s constant. If you then repeat the process you’ll just keep getting 6174 over and over again.
