The Maths Topic

Well, The Maths Topic exists, but anyway…

Hraesvelg: The final dollar goes to pay the bills of staying.
25 dollars is the sum they paid to stay at the room. 2 dollars they paid to the bellboy.

Therefore, a total of 27 dollars was being paid by them. 27/3 = 9. You shouldn’t have added two to the sum they paid - Since they have already paid it!

But that is the riddle, of course…

Problem 2:

[spoiler]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 (0-9), so it’s 910=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 single-digit numbers three times! (111, 222, etc.) so we must subtract 9*2=18 to the sum, making 90+90+90-18=252 numbers.
The remaining ones are therefore (999-100+1) - 252 = 900 - 252 = 648.[/spoiler]

Problem 3:[spoiler]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.[/spoiler]

Not having math problems but I found a few interesting mathematical stuff :tongue:

You can for example turn around 1212=144 to 441=2121

Same thing goes for 1313=169|961=3131 or 1111=121|121=1111 :razz:

The answer to everything^2 is 1764 :tongue: and 1337^2 is 1787569 :grin:

Im trying to find more funny patterns :happy:

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. :tongue:

the gravitational pull of a planet compared to earth is 3:8 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 :tongue:

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. :wink: :grin: )

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?

lets find the determinant of [A]!! :smile:
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[6-24] + 1[6-6]
=5[-18] + 0
= -90!!!

yayy!!

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

God, I’m still in Geometry and High school O_o, so I dunno what’s going on here ^_^.

Best I know?

3x-2 is parallel to 3x-12 on a grid. :happy:
-1/3x + 17 is perpendicular to 3/1x + 1,000 on a grid. (I think anyways, still a freshmen in high school :razz:)

<.< >.>

I don’t know much either.
Except the Infinity - Infinity isn’t indeterminate. It’s 0. :smile:

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?

342 Pixels? :grin:

haha lol no its just an example :tongue:

Explain.

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. :grin:
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.

Something subtracted by itself is always 1.
edit: oops my fault, meant divided.

In my opinion Infinity+5=Infinity+5 just like x+5=x+5, even tho nothing is bigger then infinity…

You mean divided, don’t you?

I didn’t know 5-5=1

Infinity is only a symbol, mainly used in limits of a sequence. Its meaning is “this sequence, while composed of finite numbers, is approaching infinity, which means the generic term of this sequence will become greater than any number”, and by generic term i mean every term of the sequence from some point onward.
Example: 5,4,10,9,15,14,20… is a sequence of numbers, and if it goes on like this (adding 6, then subtracting 1) it is approaching infinity. For example, it will be bigger than 1000 from the 401st number on, it will be greater than 1000000 from the 400001st number on, etc.

Precisely. In other words, the infinity symbol represents growth without limit.

AAAARGH! Never, ever, ever think that mathematics are defined by opinion. Mathematics is the most pure field of science existing, and does not depend on opinion at all. Tosxychors gives a nice explanation what infinity “represents” (it’s not a number) in his post above.

[size=59]And a number x € C subtracted by itself is 0, not 1.[/size]