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    16 Maths Facts That Will Make You Go "No Way"

    No calculator required.

    1. (6 × 9) + (6 + 9) = 69

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    Nice.

    2. In a room of just 23 people there’s a 50% chance that two people have the same birthday.

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    This is called the Birthday Problem, but it's only really a problem if they both want to throw parties on the same night.

    3. 111,111,111 × 111,111,111 = 12,345,678,987,654,321

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    ~ spoeky ~

    4. A pizza that has radius "z" and height "a" has volume Pi × z × z × a

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    It's important to calculate exactly how much pizza you're getting for your money.

    5. If you take any four-digit number and follow these steps, you'll end up with 6,174.

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    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.

    Eventually you'll end up at 6,174, which is known as Kaprekar's constant. If you then repeat the process you'll just keep getting 6,174 over and over again.

    6. The word "four" has four letters.

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    oooOooOooooOoooooo

    7. And the word "forty" is the only number that has all its letters in alphabetical order.

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    And one is the only number with its letters in reverse alphabetical order.

    8. 10! seconds is exactly 6 weeks.

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    OK, so for this one to be impressive you need to know what the "!" means if you don't already. It means you multiply the number (in this case 10) by one less than itself (9) and keep doing that until you get to 1. In this case: 10 x 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 = 3,628,800. And 3,628,800 seconds is EXACTLY six weeks.

    9. The number 5,040 is divisible by exactly 60 different numbers.

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    BONUS FACT: Plato considered 5,040 the best number of citizens to have in a state because of this.

    10. There are 43,252,003,274,489,856,000 ways to scramble a Rubik's Cube.

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    That number would increase by 12 if you started dismantling the cube and putting it back together in different ways.

    11. There are 80,658,175,170,943,878,571,660,636,856, 403,766,975,289,505,440,883,277,824,000,000,000,000 ways to arrange a pack of cards.

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    That's quite a lot of ways.

    12. So, if you shuffle a pack of cards properly, chances are that exact order has never been seen before in the whole history of the universe.

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    Strange but true.

    13. If you convert the phrase "How I wish I could calculate pi" into a number, it spells out the first seven digits of pi.

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    "How" contains three letters, "I" contains one, "wish" contains four, and so on. There are longer mnemonics too if you want to remember more digits.

    14. If you add up the squares of the first seven prime numbers, you get 666.

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    2² + 3² + 5² + 7² + 11² + 13² + 17² = 666.

    15. "TWELVE PLUS ONE" is an anagram of "ELEVEN PLUS TWO".

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    And, obviously, they both equal 13.

    16. 0.999999... = 1

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    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....