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#526 Re: Jai Ganesh's Puzzles » Series and Progressions » 2015-12-21 03:15:06

Just a start:

20d + 5x = 17d + x
x = -3d/4
Where x is the 0th term (a = x + d = d/4).

Sum of first seven terms: 91d/4

Oh that's a bit more than a start haha smile

Fun fact: The 17th and 82nd terms are also in the ratio 1:5. And the difference 82 - 17 is 5 times the difference between 17 - 4. Perhaps a new question is to show the next 3 predicted instances of this apparent pattern to try to confirm it! tongue

#527 Re: Puzzles and Games » The Achilles diary paradox » 2015-12-21 02:59:53

I would always be interested in having a substantive discussion smile We could start a thread about the size and/or divisibility of the universe, but I would be obliged to mention that even though I've discussed it and it is popular at least in amateur philosophy, I believe it is a question that belongs in the domain of physics rather than intuitive argument. For the latter part, though, I should at least mention that a finite universe seems more likely to me because of the irreconcilability with intervals that you pointed out, because it appears to me to be simpler by making fewer assumptions about things too small or distant to perceive, and because a continuous universe also seems to me to be unverifiable. This, the fact that a length has been identified smaller than which the current physical model of length has no meaning, and the model of the universe as expanding at a finite rate from a fixed point constitute my case in brief. But as I said, I definitely find it mathematically possible to reconcile points and intervals nonetheless, so I would not presume to know.

You will probably have to explain to me the significance of our measurements. I know that it is suggested that they are limited in principle, but compared to most I never found this fact very interesting; it says something about us and our methodology, not necessarily the structure of the world. I used to be a resolute determinist, and occasionally somebody would mention Heisenberg's uncertainty to refute it. But the fact that we do not have the power to predict something hardly seems crucial to whether it is essentially fixed or subject to probability.

#529 Re: Jai Ganesh's Puzzles » Series and Progressions » 2015-12-21 00:13:47

Hi ganesh, the series you have written for #162 is 4n + 7, so only term 1 is the same.
The 20 terms are actually 11, 7, 3, -1, -5, -9 ... -57, -61, -65. Their sum is -540. I don't know how the answers diverged so widely, but I am absolutely sure of this one.
Regarding the formula, all you have to do is change d to -4 instead of +4.

#532 Re: Help Me ! » Geometry Problem » 2015-12-20 14:57:09

Yes, that is it! Excellent smile
The only distance that is not given is AE = PR, but I'm sure it is reasonably well-known that 1-1-√2 is a Pythagorean triple since the hypotenuse is √(1^2+1^2) = √2.
Is there any restriction on the flight of the flies? Because if not, they can just fly from A directly to C. That distance has to be √2 as well, or about 1.4142, since it is completely symmetric to the distance AE. Because there is so much information provided, you can prove this with any rule you like (drawing AC on the left gives two triangles, each with 90, 45, 45 degree angles and two sides of length 1).

The ant, since that is the simpler, will prefer to walk AP + PC. The length PC is √5 / 2, since that is √(1^2+(1/2)^2), which is about 1.1180. Therefore AP + PC = 1/2 + √5 / 2 which is about 1.6180.
You can prove this simply by asserting that PC is the shortest distance from P to C and that PC + AP must be shorter than the sum of AE or AR and any available route (in fact, it is shorter than even AE + ER or AR + anything else (AR is 1.5)).

The termite is more complicated. The problem is to optimise the distance AX + XC where X is some point on PR. It's possible that this cannot be less than 1/2 + √5 / 2, and the termite will go the same way as the ant, but I haven't proved it yet.
AX = √(2x^2 + 1/4) where x is the fraction of the distance PR traveled from P (in other words, x = PX/PR).

#533 Re: Help Me ! » Geometry Problem » 2015-12-20 06:21:54

I, personally, cannot tell just how the triangular block has been cut yet, and I like word problems. If you cannot give a link, can you email a file? If not, perhaps you could describe the layout of the triangular cut in more detail, specifically the lines connecting A to C? Sorry that I cannot see it just yet (:

#534 Re: Computer Math » Absorbing Markov Chains reloaded » 2015-12-20 02:51:24

I am very ignorant of higher maths and will be unable to shed much light on this problem, but just to get the ball rolling I think it's clear that it must be more than 12 (since there is greater than a 50% chance of winning the first 6 and that guarantees a minimum 12).

#535 Re: Jai Ganesh's Puzzles » Interesting Information..... » 2015-12-20 01:18:29

62. I know that Earth is about 1 trillion cubic km. I know the Sun is something like 99.9% of the mass of the solar system. I know Jupiter is about 300 times larger than Earth. I guess that there is roughly 5 or 6 Jupiters' worth of mass in the rest of the Solar System (minus the Earth and Sun). Which puts the Earth at between one 1500th and one 1800th of one tenth of one percent of the Solar System, while the Sun is virtually all of it. I therefore estimate the volume of the Sun to be at least one and a half million and maybe 1.8 million times that of the Earth, or about 1.5 to 1.8 * 10^18 cubic km. How did I do? (:

#537 Re: Jai Ganesh's Puzzles » Oral puzzles » 2015-12-20 00:24:39

There seem to be a lot of questions toward the start of this thread that have never been answered.

#538 Re: Jai Ganesh's Puzzles » Oral puzzles » 2015-12-20 00:06:49

Hi!


Although I never actually bothered to learn the short-cut method with frequencies ;s
Median is 70. Standard deviation is √(345/11) / 2 ~ 2.8002

#540 Re: Puzzles and Games » The Achilles diary paradox » 2015-12-19 23:31:22

Although I think it is mathematically possible that we are in some sense crossing infinity when we walk across a room, or even situated within an infinite cosmos, philosophically I find it more probable that space is finite, and composed of units that the Ancient Greeks would have called "atoms" but perhaps what we call Planck lengths or quantums of length.

That is from the perspective of infinity, not necessarily from his own perspective (: It seems possible to me that the long spans of time between could diminish the effect of the undesired non-birthday. But then any speculation about what it is like to live forever is quite suspect. Just now I was thinking that perhaps immortality would not be so bad if you could ensure that you don't remember the same thing twice, only to lose myself in the idea that if one experiences every physical event in a finite space, they also experience every psychological one.
Even though I understand it, the fact still is quite strange, and morbid, that eventually everyone would choose to die.

Yes we could get into some trouble, since I have spent a lot of time on forums discussing philosophy and you have a strong interest in paradoxes involving the infinite xD

#541 Re: Puzzles and Games » Multiply by the next consecutive number. » 2015-12-19 22:43:50

Wow, that seems rather obvious now. Thank you very much! smile

123 * 56! = 87452826299998204578047614638038168817589251402383720418555985920000000000000 ~ 8.75 * 10^76 ~ 87.5 quattuorvigintillion

The posts were absolutely correct, incidentally.

#542 Re: Jai Ganesh's Puzzles » General Quiz » 2015-12-19 22:02:32

Just an alert that the answer to #5724 is stated in the question smile

#543 Re: Puzzles and Games » Multiply by the next consecutive number. » 2015-12-19 21:55:47

I confirmed the first 15 digits of my own term for this sequence, and the first three digits of a few others. I suppose that is confidence enough. Can anyone show me how to write an explicit formula for a sequence like this?

~28.4 trevigintillion * 55 = 1561657612499967938893707404250681586028379489328280721759928320000000000000 or approximately 1.56 * 10^75 which is about 1.56 quattuorvigintillion.

#545 Re: Puzzles and Games » The paradox of the infinite pyramid scheme » 2015-12-19 19:24:59

Just to be pedantic, the occupant of room 1 would get N - $1, since his own contribution goes to himself. But your point still works fine with most any similar arrangement, and I'm not sure guest 1 would gripe about the lost dollar with a limitless N! smile A neat consequence of infinite individuals with any positive wealth!
Or any positive amount of anything for that matter. In principle, if there are infinitely many people with any amount of something and the ability to transfer that something in a chain (it need only be one-way), then they can all acquire a limitless amount of it simply by redistribution (bounded only by time, perhaps).

#548 Re: Puzzles and Games » The Achilles diary paradox » 2015-12-19 18:38:10

Infinity is fun, isn't it? I have always thought so haha!

Once again, I don't think that it is much of a problem. If it isn't agreed otherwise, he can in fact always reply "Not yet!", because there will never come a day when it is declared that he cannot take all of the non-birthday pages with the pattern he is obeying.
I'm also not sure that Achilles would mind much if he was ordered to specify his page-tearing routine. He would just have to come up with a way of describing the largest possible finite number of days he can after which he is obligated to take a non-birthday page. And even if he only had a day to do so, he would be able to come up with a truly immense number. But then again, he would still have to suffer an infinite number of non-birthdays, so it's possible this is little compensation after all!

To be honest, I think that being immortal is the most frighteningly horrifying prospect imaginable, no matter what special powers you are given. To live until everything that could possibly happen in a finite space has happened, and then to do it again, and again, and again...

Zeno's spatial paradoxes once troubled me too, but eventually I got an explanation that satisfied me. Basically, very small distances are traversed in very small amounts of time, so time makes velocity possible. Zeno probably thought of time and motion as the same.

#550 Re: Jai Ganesh's Puzzles » Oral puzzles » 2015-12-19 17:53:09

Yet again there are various solutions for this type of problem, yet clearly we are only expected to give the obvious one. That one is


Other solutions are (by substituting every combination of solutions): 1/5 and +/-4/5.

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