Current Events > What's your favorite math fun fact?

(+) Yeah! (+)

If you multiply any number by 5 and move the decimal point to the left, you've found its half.

For example, 50 X 5 = 250.0 move the decimal to the left and you have 25 which is half of 50

Alternatively, if you halve any number and add a 0 or move the decimal point right, you've found its multiple of five.

So 43 / 2 = 21.5, move the decimal point to the right and it's 215 which is what 43 X 5 is.

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I can't stand math

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Til 0.5 is just 5 with the decimal moved to the left lol!

Personally I like how each multiple of 9, if you add up the digits, they equal 9

9x2 =18 (1+8 =9)
9x3 =27 (2+7 =9)
9x4= 36 (3+6 =9)

etc

This is only for 1-10 though

Also I hate math

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In the case of an undeformed state, the relative right Cauchy-Green tensor C_t takes in the value of the unit tensor 1 as opposed to 0 as one might assume through intuition
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you're saying multiply by 5 and divide by 10 instead of just divide by 2 >_>

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AlCalavicci posted...

This is only for 1-10 though

False
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I before e except after C is a fucking lie

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tagging the math nerds in this topic so i know who to give a wedgie to in the schoolyard later

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Anything + 0 is always itself, idk something about that concept was always pretty cool

like 0 is nothing but is also something at the same time

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teepan95 posted...

False

How so?

9x11 = 99 ( 9+9 =/= 9)

I didn't go beyond that

Edit: Oh snap, how far does this go??

9x12 = 108 (1+0+8 = 9)

Even cooler!

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AlCalavicci posted...

This is only for 1-10 though

No. It works on all.

Example-129=108

1+0+8=9


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SSJGrimReaper posted...

tagging the math nerds in this topic so i know who to give a wedgie to in the schoolyard later

Hell yeah bro. High five.

See ya, nerds.

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Bishop9800 posted...

No. It works on all.

Example-129=108

1+0+8=9

Very cool. 9x11 must be the exception

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AlCalavicci posted...

How so?

9x11 = 99 ( 9+9 =/= 9)

I didn't go beyond that

i honestly can't tell if you're fucking with us.

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AlCalavicci posted...

Very cool. 9x11 must be the exception

No...
9x11=99

9+9=18

8+1=9

It always comes back to 9

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Bishop9800 posted...

No...
9x11=99

9+9=18

8+1=9

It always comes back to 9

Yeah, I mean I wasn't actually considering taking that extra step, so I guess you're right in that sense. I guess my original point was that it comes back to 9 just by adding the digits that first initial time. In this case you're adding the digits the second time too to get to 9. Which is cool that it still works that way


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We once had a guest lecturer from the math department where he spent almost the entire class going through some bullcrap proof where he said it was possible to divide by zero.

We never heard from him again.

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Euler's identity

e^(i pi) + 1 = 0

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If you type 55378008 on a calculator it spells BOOBLESS. Upside down.

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Naysaspace posted...

Til 0.5 is just 5 with the decimal moved to the left lol!

that makes the fun fact slightly less fun

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https://www.youtube.com/watch?v=xCtRPtjGGXI

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6 x 9 + 6 + 9 = 69

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Kinda confusing to explain...To find out if a number is a multiple of 9, add up the numbers, and if it's a multiple of 9, then the original number is too. Like 81 is 8+1 = 9, so it's a multiple of 9. 5,436 is 5+4+3+6 = 18, so it's also a multiple of 9 since 18 is a multiple of 9.

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You can find out if a number is divisible by 3 if you add up all the digits and come up with a number divisible by 3. You can run the step again too and add all the digits of THAT result.
For example: 999 -> 9 + 9 + 9 = 27 -> 2 + 7 = 9

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The 9 multiplication table pattern, but I can't explain it well. But if you know it you know it.

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For almost all real numbers x, if you take the geometric mean (the nth root of the product of n numbers) of the coefficients of the continued fraction of x, you end up with a finite number, independent of x, called Khinchin's constant.

That's not the fun fact. The fun fact is that despite this being true for "almost all real numbers", we have never found any number that this is true for except for those specifically constructed to have it be true.

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The product of four consecutive integers, plus 1, is always a perfect square, no matter where you start.

ex: (1x2x3x4)+1 = 25 = 5^2


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Any number is divisible by 3 if you add all the digits and that number is also divisible by 3.

For example: the number 12.345. If you add all digits you get 1 + 2 + 3 + 4 + 5 = 15. And 15 is divisble by 3.

So any random large number can easily indentified whether divisible by 3. Like: 462.591 (which is 27 if you add all digits).

This has always stuck with me for some reason.

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E

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The quadratic formula is kinda cool

If you take any 3-digit number divisible by 37 and move the front digit to the back, or vice versa, the result will also be divisible by 37. For example, 4*37 = 148. 481 and 814 are also divisible by 37.

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If you enter Pi two decimal places (3.14) in your calculator and look at it in the mirror, you'll see it spells 'pie'

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DuranOfForcena posted...

i will forever remember the quadratic formula, literally to my dying day, because of my 11th grade Algebra 2/Trig teacher Mr. Albert and the mnemonic device he taught us to remember it by, which is setting the recitation of it to the tune of Pop Goes the Weasel.

same

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If you write 58008 in a calculator and turn it upside down, it says boobs

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Percentages work both ways. 10% of 15 is the same as 15% of 10.

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2 + 2 = 5

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It blew my mind when I first learned about integrals, and found out that the space under a curve on a graph actually has significance

Also that when you learn the y = mx + b stuff in algebra, and they teach you about the slope m, you've already learned the basics of differentiation

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Why dont you and I add up, subtract our clothes, divide your legs, and multiply

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