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30

Posts: 2415 Joined: 11 Jul 2009 Last Visit: 30 Dec 2013
LD count: d(LD)/dt>0
Location: Present Moment  


Posted: Sat 17 Oct, 2009 


Problem 2:
Click here to see the hidden message (It might contain spoilers)
The possibility for two repeated digits is, the 1° and the 2° (xxy), the 1° and the 3° (xyx), the 2° and the 3° (yxx);
First case: the 1° digit (the hundreds one) has 9 possibilities (from 1 to 9), the 3° one is free and can be 10 numbers (09), so it's 9*10=90 numbers
Same with the second case: 90 numbers.
For the third case, first digit can be 9 numbers, the other two can be 10, so it's still the same: 9*10= another 90 possibilities.
But wait! We counted the singledigit numbers three times! (111, 222, etc.) so we must subtract 9*2=18 to the sum, making 90+90+9018=252 numbers.
The remaining ones are therefore (999100+1)  252 = 900  252 = 648.
Problem 3:
Click here to see the hidden message (It might contain spoilers)
After spending on clothes, she has half the money left; after games, it's 1/2  (1/2 * 1/3) = 1/3; after toys, it's 1/3  (1/3 * 1/4) = 1/4 money left.
So it's x/4=7777, so x = 21108, where x is yearly allowance. To get a single month, we do x/12= 7777/3 = 2592,33.
Current LD goal(s): Healing



 
 
   




27 
Posts: 4392 Joined: 17 Feb 2008 Last Visit: 01 May 2017
LD count: Loads of them
Location: lost  


Posted: Sun 18 Oct, 2009 


Not having math problems but I found a few interesting mathematical stuff
You can for example turn around 12*12=144 to 441=21*21
Same thing goes for 13*13=169961=31*31 or 11*11=121121=11*11
The answer to everything^2 is 1764 and 1337^2 is 1787569
Im trying to find more funny patterns
Current LD goal(s): Become a firemaster



 
 
   





Posts: 523 Joined: 25 Sep 2006 Last Visit: 24 Mar 2018
LD count: Thrice a week
 


Posted: Mon 19 Oct, 2009 


Something notable is that
[13.37 * pi] = 42
where [x] denotes the largest possible integer that is < x. Actually, even without the [], it is accurate to two decimals.



 
 
   




24 
Posts: 346 Joined: 29 May 2009 Last Visit: 22 Nov 2011
Location: California  


Posted: Mon 19 Oct, 2009 


the gravitational pull of a planet compared to earth is 3 or 3/8 a new moon starts to orbit the other planet making the gravitational pull 5x stronger what is the new ratio? it took me a while to figure that out myself



 
 
   




151

Posts: 2504 Joined: 21 Jul 2008 Last Visit: 12 Oct 2019
LD count: %d
Location: Prism Stone  


Posted: Mon 19 Oct, 2009 


Math/Physics Problem... Solve it for cookies.
(Let's just say that 1g = 9.8 m/s^2 instead. That is equal to 9.8 newtons of force per square kilogram. )
You drop a 1000kg object from 1km high. If it were to fall at a steady rate of 9.8 meters per second, how much force will it undergo when it hits the ground?
Current LD goal(s): Get a real LD; Shoot fireworks out of my hands; Become top idol
Link to My DJ: www.ld4all.com



 
 
   




26

Posts: 578 Joined: 09 Apr 2008 Last Visit: 24 Aug 2013
 


Posted: Mon 19 Oct, 2009 


lets find the determinant of [A]!!
1 3 4
[A]= 2 6 2
5 0 1
Expand row 3!!
3 4 1 3
5  6 2 + 1  2 6
=5[3(2)6(4)] + 1[1(6)2(3)]
=5[624] + 1[66]
=5[18] + 0
= 90!!!
yayy!!



 
 
   





Posts: 523 Joined: 25 Sep 2006 Last Visit: 24 Mar 2018
LD count: Thrice a week
 


Posted: Mon 19 Oct, 2009 


Mew151 wrote: 
Math/Physics Problem... Solve it for cookies.
(Let's just say that 1g = 9.8 m/s^2 instead. That is equal to 9.8 newtons of force per square kilogram. )
You drop a 1000kg object from 1km high. If it were to fall at a steady rate of 9.8 meters per second, how much force will it undergo when it hits the ground? 
It depends on how long the collision lasts. Longer lasting collisions will result in a smaller average force. The impulse, however, can be calculated:
kinetic energy = 0.5 * mass * velocity^2
potential energy = mass * gravitational acceleration * height
kinetic energy = potential energy
0.5 * mass * velocity^2 = mass * gravitational acceleration * height
velocity = sqrt(2 * gravitational acceleration * height)
impulse = difference in momentum
difference in momentum = final momentum  initial momentum = mass * (0  initial) = mass * sqrt(2 * gravitational acceleration * height) = 1000 * sqrt(2 * 9.8 * 1000) = 140,000 Ns



 
 
   

RoDRuler of Dreams



24 
Posts: 116 Joined: 15 Aug 2009 Last Visit: 31 Mar 2010
LD count: Like 3
Location: In my dreams  


Posted: Mon 19 Oct, 2009 


God, I'm still in Geometry and High school O_o, so I dunno what's going on here ^_^.
Best I know?
3x2 is parallel to 3x12 on a grid.
1/3x + 17 is perpendicular to 3/1x + 1,000 on a grid. (I think anyways, still a freshmen in high school )



 
 
   




151

Posts: 2504 Joined: 21 Jul 2008 Last Visit: 12 Oct 2019
LD count: %d
Location: Prism Stone  


Posted: Mon 19 Oct, 2009 


<.< >.>
I don't know much either.
Except the Infinity  Infinity isn't indeterminate. It's 0.
Current LD goal(s): Get a real LD; Shoot fireworks out of my hands; Become top idol
Link to My DJ: www.ld4all.com



 
 
   




24 
Posts: 346 Joined: 29 May 2009 Last Visit: 22 Nov 2011
Location: California  


Posted: Tue 20 Oct, 2009 


how long is the piece of string 
A: since you dont know the exact length its the amount it takes for the right side to get to the left side(vice versa)multiplied by two, right?



 
 
   




151

Posts: 2504 Joined: 21 Jul 2008 Last Visit: 12 Oct 2019
LD count: %d
Location: Prism Stone  


Posted: Tue 20 Oct, 2009 


Scarface wrote: 
how long is the piece of string  
342 Pixels?
Current LD goal(s): Get a real LD; Shoot fireworks out of my hands; Become top idol
Link to My DJ: www.ld4all.com



 
 
   




24 
Posts: 346 Joined: 29 May 2009 Last Visit: 22 Nov 2011
Location: California  


Posted: Tue 20 Oct, 2009 


Mew151 wrote: 
Scarface wrote: 
how long is the piece of string  
342 Pixels? 
haha lol no its just an example



 
 
   




27 
Posts: 493 Joined: 03 Feb 2007 Last Visit: 16 Dec 2009
LD count: 4
 


Posted: Tue 20 Oct, 2009 


Mew151 wrote: 
Except the Infinity  Infinity isn't indeterminate. It's 0. 
Explain.



 
 
   




151

Posts: 2504 Joined: 21 Jul 2008 Last Visit: 12 Oct 2019
LD count: %d
Location: Prism Stone  


Posted: Tue 20 Oct, 2009 


Hmmm...
Well, Infinity, subtracted by itself, should be zero.
Because even though it is unlimited, no further numbers exist.
So even though Infinity + 5 = Infinity, Infinity = Infinity, never something greater, because nothing greater exists. So just treat Infinity like a number.
So Infinity  Infinity = 0.
If it is true, Infinity  Infinity  Infinity = Infinity, because 0  Infinity = Infinity.
Current LD goal(s): Get a real LD; Shoot fireworks out of my hands; Become top idol
Link to My DJ: www.ld4all.com



 
 
   





Posts: 523 Joined: 25 Sep 2006 Last Visit: 24 Mar 2018
LD count: Thrice a week
 


Posted: Tue 20 Oct, 2009 


Mew151 wrote: 
Hmmm...
Well, Infinity, subtracted by itself, should be zero.
Because even though it is unlimited, no further numbers exist.
So even though Infinity + 5 = Infinity, Infinity = Infinity, never something greater, because nothing greater exists. So just treat Infinity like a number.
So Infinity  Infinity = 0.
If it is true, Infinity  Infinity  Infinity = Infinity, because 0  Infinity = Infinity. 
There is no number such as infinity. And even it there were, it would not hold under arithmetic axioms.
I'll have to repeat: There is no "infinity" number.



 
 
   
 
 