|One really frustrating knitting project.|
WARNING: For the math nerds amongst us.
You have been warned.
Math LimerickA dozen, a gross, and a score,Math Limerick by Bellairs
Plues three times the square root of four,
Divided by seven,
Plues five times eleven,
Is nine squared, and not a bit more
Magic Number 9Magic Number 9Magic Number 9 by Bellairs
I've never thought a number could be great, but 9 is pretty damn useful.
If you're unsure if a number is divisable by 9, add together its digits. If the sum of its digits is divisable by 9 then so is the entire number.
Is 56975373 divisable by 9? Add up the digits to get 45. So yes, it is divisable 9, and the answer is 6330597.
This trick is for multiplying with numbers like 99 or 99999999.
Say you need to multiply 20956 by 99999 manually. The answer is:
(20956-1) | (100000-20956) =
20956 | 79044 =
Or: 47 X 99
(47-1) | (100-47) =
46 | 53 =
Multiply any number by 9. Take the product and add the digits together to get another multiple of 9. Add the digits together again to get ANOTHER multiple of 9. If you repeat this enough times you'll eventually get to 9.
9 × 9 = 81
8 + 1 = 9
56231873561843 x 9 = 506086862056587
5+0+6+0+8+6+8+6+2+0+5+6+5+8+7 = 72
7+2 = 9
About Me:See that hedgehog? Well, that's me. Or at least according to my friend the cat. (Full disclosure: I don't see the resemblance, myself...)|
Edit: She's changed her mind. She now claims I'm a caribou. Sheesh! Besides, hedgehogs are cuter.