You math nerds clearly like to throw the jargon around as if to impress people. I find nothing more unimpressive than scientific abstractions. Try some social science and really learn about the world around you!
I hate social workers who keep trying to help you, like there's something wrong.
Somebody once said social workers were girls that couldn't type. Haha. 
- Jul 29, 2001
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Originally posted by: Howard
I hate social workers who keep trying to help you, like there's something wrong.
I know a girl who is applying for social work at school.... and she can't type
Originally posted by: silverpig
Originally posted by: Howard
I hate social workers who keep trying to help you, like there's something wrong.
I know a girl who is applying for social work at school.... and she can't type
Now I know who said it - David Eddings, through his character Damon Flood in The Losers.I bought this math kit by Scott Foreman (I think that's the name) when I was little - I really liked it. But it only shows you how to do basic math quickly - (addition/subtraction/division/multiplication). The multiplication one was really effective.
I only remember how to do a two digit times digit one:
12
13
---
Multiply first column (3 x 2 = 6) - write that down in one's column
Multiply diagonally (2 x 1) and (1 x 3) add those together to get 5; write that down in tens column
Multply tens digits 1 x 1 and that will be the hundreds digit.
You get 156
I only remember how to do a two digit times digit one:
12
13
---
Multiply first column (3 x 2 = 6) - write that down in one's column
Multiply diagonally (2 x 1) and (1 x 3) add those together to get 5; write that down in tens column
Multply tens digits 1 x 1 and that will be the hundreds digit.
You get 156
ok, here two:
------------
first one, easy way to calculate squares up to about 125^2 in tha head.
it works quite well if you still kind of remember the squares up to 25^2 from math-class. the formula is simple: x^2=(x+y)*(x-y)+y^2
the idea is to either make the (x+y) or the (x-y) something easy to multiply with.
examples: 11^2=12*10+1 (just as how-to)
63^2=76*50+13^2=3800+169=3969
97^2=100*94+3^2=9400+9=9409
124^2=148*100+24^2=14800+576=15376
it's easiest if you get to multiply with 20, 50 and 100.
------------
other one: 3rd root (is that english? i mean x^(1/3)) of a 4-6 digit number (asumed it results a integer) in tha head.
things to remember:
1 x 1 x1=1
2 x 2 x 2=8
3 x 3 x 3=27
4 x 4 x 4=64
5 x 5 x 5=125
6 x 6 x 6=216
7 x 7 x 7=343
8 x 8 x 8=512
9 x 9 x 9=729
the idea is, that the 3rd root (i just call it that way) is a 2 digit-number.
first step: forget the last 3 digits. and chose the number from the list nearest under the left digits.
ex: 300 763^(1/3). forget last 3 digits->300 nearest one under 300 is 6^3=216, so the first digit of the result is a "6".
for the second digit of the result things to remember:
if the last digit of the given number (here 300763) ends on a 0, 1, 4 , 5 , 6 or 9, just take it as the result for the second digit.
if the last digit of the given number ends on 2, 3, 7 or 8, the result for the second digit is 10-(last digit).
in the example: 300763 end on "3" so the second digit of the result is (10-3)=7
so the third root of 300763=67
i hope you got it from my cranky english, but once you got the principles it's quite easy:
ex: 614125^(1/3)=
614->512->"8" as first digit of result.
614125 ends on 5= second digit of result
614125^(1/3)=85
----------------
oh well... whatever... first one is quite a practical, second is something for nerd-partys...
(why do i still remember this sh147? it was like 10 years ago when i thought about such stuff (second one was on tv (no, not a US-channel and not BBC-learning )...)
note to self: stop posting...
------------
first one, easy way to calculate squares up to about 125^2 in tha head.
it works quite well if you still kind of remember the squares up to 25^2 from math-class. the formula is simple: x^2=(x+y)*(x-y)+y^2
the idea is to either make the (x+y) or the (x-y) something easy to multiply with.
examples: 11^2=12*10+1 (just as how-to
)63^2=76*50+13^2=3800+169=3969
97^2=100*94+3^2=9400+9=9409
124^2=148*100+24^2=14800+576=15376
it's easiest if you get to multiply with 20, 50 and 100.
------------
other one: 3rd root (is that english? i mean x^(1/3)) of a 4-6 digit number (asumed it results a integer) in tha head.
things to remember:
1 x 1 x1=1
2 x 2 x 2=8
3 x 3 x 3=27
4 x 4 x 4=64
5 x 5 x 5=125
6 x 6 x 6=216
7 x 7 x 7=343
8 x 8 x 8=512
9 x 9 x 9=729
the idea is, that the 3rd root (i just call it that way) is a 2 digit-number.
first step: forget the last 3 digits. and chose the number from the list nearest under the left digits.
ex: 300 763^(1/3). forget last 3 digits->300 nearest one under 300 is 6^3=216, so the first digit of the result is a "6".
for the second digit of the result things to remember:
if the last digit of the given number (here 300763) ends on a 0, 1, 4 , 5 , 6 or 9, just take it as the result for the second digit.
if the last digit of the given number ends on 2, 3, 7 or 8, the result for the second digit is 10-(last digit).
in the example: 300763 end on "3" so the second digit of the result is (10-3)=7
so the third root of 300763=67
i hope you got it from my cranky english, but once you got the principles it's quite easy:
ex: 614125^(1/3)=
614->512->"8" as first digit of result.
614125 ends on 5= second digit of result
614125^(1/3)=85
----------------
oh well... whatever... first one is quite a practical, second is something for nerd-partys...
(why do i still remember this sh147? it was like 10 years ago when i thought about such stuff (second one was on tv (no, not a US-channel and not BBC-learning
)...)note to self: stop posting...
"I bought this math kit by Scott Foreman (I think that's the name)..."
Scott Flansburg actually. Art Benjamin has a Mathemagics book out that is pretty good. There is also an old old book out there called How to Calculate Quickly that is good too.
I always liked this one: instantly squaring two digit numbers that end in 5.
45^2 = 2025
65^2 = 4225
x5^2 = x*(x+1), with 25 tacked on to the end.
Scott Flansburg actually. Art Benjamin has a Mathemagics book out that is pretty good. There is also an old old book out there called How to Calculate Quickly that is good too.
I always liked this one: instantly squaring two digit numbers that end in 5.
45^2 = 2025
65^2 = 4225
x5^2 = x*(x+1), with 25 tacked on to the end.
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