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> Need some math tricks + something else...
XeroCool
post Jan 29 2006, 08:19 PM
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My math teacher always likes some kind of math things to solve. It can be about anything. I was wondering If any of you know any math websites, that show some kind of hard things to solve or do. Also, Im looking for some pictures where you have to draw it without taking your pencil off your paper, and without re-tracing the lines. I like those those things, and my teacher loves it too. I dont mean to sound like a noob or anything, but I find math cool. msn_happy.gif
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Khyshen
post Jan 29 2006, 08:50 PM
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www.bbc.co.uk/schools

Lol I know some math tricks
how about to find out what goes into the 3 times table

to find out if 36 is in the 3 times table we simply have to do this
add the two numbers together... 3+6 = 9
so, anything that goes into the 3 times table means that it is in the 3 times table:D

some e.gs 75 , 7+5 =12 , 12 does go into the 3 times table does it? yea
56 , 5+6 = 11, 3 doesent go into 11 does it...

lol help from a 12 year old.... <.<
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Russ
post Feb 4 2006, 09:04 AM
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also if (sinx)˛x(cosx)˛=1˛ x can be any number between 0.1 to 89.9

This post has been edited by Russ: Feb 4 2006, 09:05 AM
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~!~Alou$hka~!~
post Feb 4 2006, 09:32 AM
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well heres a cool one...
if an angle i less than 15 degrees x=13 degrees
sinx = x but in radiant
tanx = x also in radiant

sin13 = 0.226
to know how to go from radiant to degrees this is wat u have to
∏ 180 degrees
0.226

0.226 radiant = 0.226*180 / 3.14 = 13 degrees

lol sumtimes in exAms it saves time msn_happy.gif

This post has been edited by ~!~Alou$hka~!~: Feb 4 2006, 09:34 AM
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Khyshen
post Feb 4 2006, 11:03 AM
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I know one for Pi = ∏ [Pi]

To find circumference of a circle
do

∏ x Radius = Circumference of Circle
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Gaz™
post Feb 4 2006, 12:16 PM
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first off, its radians on radiants.

seconds off, to find out the multiple of 9, say 5*9, you take 1 away from the 5, to get 4, then take the 4 away from 9 to get 5, so the answer is 45.

another example 12*9, 11, 11-9=-2

110 - 2, = 108 msn_wink.gif

and did you know that the coefficient of friction * normal reaction = Friction.
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ice_king
post Feb 4 2006, 12:31 PM
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(sin)x = 1-(cos)x
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Abhimanyu
post Feb 4 2006, 12:57 PM
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QUOTE(Craven-Image @ Feb 4 2006, 04:33 PM)
I know one for Pi = ∏ [Pi]

To find circumference of a circle
do

∏ x Radius = Circumference of Circle
[right][snapback]120403[/snapback][/right]

its actually 2 x ∏ x radius.

Edit: wat evrybody is writing rae not tricks.. but mathematical formulae and functions..

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Volv
post Feb 4 2006, 12:57 PM
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QUOTE
(sin)x = 1-(cos)x

Umm that's not true, perhaps you're referring to (sin(x))^2 = 1 - (cos(x))^2 and that's not really a trick...

QUOTE
∏ x Radius = Circumference of Circle

That's not correct either Craven-Image, it's 2 x ∏ x Radius = Circumference of Circle and ∏ x Radius^2 = Area of Circle


Also, a better way of doing 9x tables is multiplying the number by 10 then subtracting that number from the result
eg:
5*9 = 5*10 - 5 = 45
12*9 = 12*10 - 12 = 108

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Gaz™
post Feb 4 2006, 01:04 PM
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thats a nice trick, but i like my way =)
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Wabz
post Feb 4 2006, 01:32 PM
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I believe the square root of minus one is equal to n
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psyko
post Feb 4 2006, 01:51 PM
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No, that can't be Wabz, because when you take the square root of a negative number, you start getting involved with Complex Numbers.

Ex. Square root of -1 = 1i

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Lord d'Eath
post Feb 4 2006, 02:01 PM
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[google]sqrt(-1)[/google]
QUOTE
sqrt(-1) = i
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plastikaa
post Feb 4 2006, 03:52 PM
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the sqaureroot of -1 is i - this is complex numbers which have 2 dimensions in theory. So you can have 3+4i as a number and that can be plotted on a graph with real and imainary axes. so 3 across and 4 up.

Therefore the modulus of 3+4i is infact the sqaureroot of (3^2+4^2) which is 5

|3+4i|=5

Also if you want not so much of a trick but something clever to know about those things "where you have to draw it without taking your pencil off your paper"

If you look at the picture and all the bits where lines join are of evenorder (eg 2,4,6,8 etc.) and no odd ones then you have what is known as a Eulerian Graph, and its definitely possible to draw the thing aswell as starting and finishing at the same point. If you have all even joins apart from 2 odd ones then you have what is called a semi eulerian graph and it can also be drawn but your start and finish will be in different places.

If you have 1 3 or more places where the joins have odd numbers of joints then you can definitely not draw it.

So next time you can save yourself time and mathematically look at whether or not its possible before you attempt it! That could suprise your teacher!
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psyko
post Feb 4 2006, 06:37 PM
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QUOTE(Lord d'Eath @ Feb 4 2006, 09:01 AM)
[google]sqrt(-1)[/google]
[right][snapback]120439[/snapback][/right]


It's the same thing as 1i, only your answer doesn't have coefficient in the front of it (as any variable by itself (Ex. x; that means 1x) has a coefficient of one in the front). msn_wink.gif

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Russ
post Feb 4 2006, 06:48 PM
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Think of a number (and don't forget it). Double it. Add six. Divide your answer by two. Now take away the number you first thought of. The number in your head is now... three!
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ice_king
post Feb 4 2006, 06:50 PM
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omg..... that works
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Gaz™
post Feb 4 2006, 06:56 PM
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obviously, you add six, then half it = 3, then takin away what u had in the first place. ur doubling and halfing cancles out, which is why u are left with 3.

basically, think of a number, double it, add 2, half it, take away the number you thought off, now u have 1.

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zero cool
post Feb 4 2006, 07:51 PM
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Fast multiplication by 11 with numbers 10 to 45.

You take for example you want to multiply 25 by 11 you add 2 and 5 and the total you get put in between the number you were multiplying 275. After number 45 you add numebrs but cince you have one digit more you give it to the 1st digit. Example 65 6 and 5
= 11 so you ad one to 5 which will be 8 then you have 1 and 5 left so total is 715.



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~!~Alou$hka~!~
post Feb 4 2006, 08:24 PM
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lol u all amateurs in maths hehe joking u call those tricks??? check this out:
Add this up in your head.....no pen or paper or calculators....

Take 1000 and add 40 to it. Now add another 1000.
Now add 30. Another 1000.
Now add 20. Now add another 1000. Now add 10.

What is the total ?




Did you get 5000?
The correct answer is actually 4100. Don't believe it?
Check with your calculator!
The decimal sequence confuses our brain, that always jumps to the
highest
decimals (100s instead of 10s)
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