Search found 1034 matches

by euler
Tue Apr 04, 2006 11:16 pm
Forum: Combinatorics
Topic: No Ones
Replies: 1
Views: 2342

No Ones

Given that r is non-negative integer chosen at random and contains no more than n digits, what is the least value of n such that the probability of r containing no ones among its digits is less than 50%? What about less than 10%, 1%, p? What about containing no twos, threes, ... ? What about no zeros?
by euler
Tue Apr 04, 2006 10:31 pm
Forum: Combinatorics
Topic: Lucky 7
Replies: 1
Views: 2247

Lucky 7

Given that n is a positive integer, find the probability that 2n – n2 is divisible by 7.
by euler
Tue Apr 04, 2006 8:00 pm
Forum: Number Theory
Topic: Mystery Function
Replies: 5
Views: 4468

Mystery Function

Explain what the following recursive function does, and why it works.

function mystery(x, y)
   r = x mod y
   if (r > 0) y = mystery(y, r)
   return y
end function
by euler
Tue Apr 04, 2006 5:05 pm
Forum: News, Suggestions, and FAQ
Topic: a Problem reading text
Replies: 1
Views: 2469

Thanks for pointing that out ThomasH. I was re-writing part of the forum code that would allow easier (from my perspective) addition of new BBCode style symbols and it caused previous posts to not display properly. I thought I had gone through and fixed them all, but clearly I had missed one. All so...
by euler
Tue Apr 04, 2006 5:02 pm
Forum: Game Theory
Topic: Shortest chess game
Replies: 19
Views: 12756

Eighty, I hope you don't mind but I edited your post to replace the [ code ] section with [ tt ], as this offers monospacing and preservation of spaces without wrapping it in a code window. As a side issue I've now just discovered that [ code ] within [ hide ] doesn't function properly: the "Expand...
by euler
Sun Apr 02, 2006 10:46 pm
Forum: Recreational
Topic: Active users??
Replies: 1
Views: 2689

Active users include those who have solved at least one problem within 180 days AND newly registered users who have not yet solved any problems yet. However, if a user registers and does not solve at least one problem within 30 days then their account is "purged". The only reason I mention the numbe...
by euler
Fri Mar 31, 2006 4:14 pm
Forum: Applied Mathematics
Topic: 0-60mph
Replies: 11
Views: 9146

I guess that there are two types of problem that may appear in the "Applied Mathematics" forum: (i) problems for which parameters are given and the challenge is to acquire the correct model (whether it be statistical or relating to mechanics), or more difficult, (ii) problems for which neither the p...
by euler
Thu Mar 30, 2006 7:27 am
Forum: Recreational
Topic: Missing Wedding Ring Finger
Replies: 15
Views: 12608

Unfortunately the double jeopardy answer is the classic one I have already tried, and it's certainly one of my favourites. So I'm afraid my torment continues. :wink:
by euler
Wed Mar 29, 2006 11:52 pm
Forum: Recreational
Topic: Missing Wedding Ring Finger
Replies: 15
Views: 12608

Missing Wedding Ring Finger

The following lateral problem has tortured my sanity for many years now. It has a classic answer, and I have personally been through numerous other plausible answers, but I've been assured by a puzzle-meister that there is another answer. Even though I've still not discovered this "other answer" it ...
by euler
Wed Mar 29, 2006 10:32 pm
Forum: Number
Topic: A mean radical puzzle
Replies: 2
Views: 3018

Hi quintic, you may be interested to know that I've just added BBCode that allows some mathematical notation to be used; more to come! Check out the topic here:
http://mathschallenge.net/forum/viewtopic.php?t=48
by euler
Wed Mar 29, 2006 10:05 pm
Forum: Number
Topic: Three ratios
Replies: 5
Views: 3821

What an interesting result, quintic! That certainly works, rlblaster. An alternative approach... As a/b = r, a = br; similarly c=dr and e=fr. Numerator, N = 3a 2 c + 4c 3 e + 3e 2 c = 3(br) 2 dr + 4(dr) 3 fr + 3(fr) 2 dr = dr 3 (3b 2 + 4d 2 fr + 3f 2 ) Denominator, D = 3b 2 d + 4d 3 fr + 3f 2 d = d(...
by euler
Tue Mar 28, 2006 11:32 pm
Forum: Number Theory
Topic: Numbers with Divisibility Conditions
Replies: 5
Views: 5961

RogerHui, as this puzzle requires a computer to solve I've moved it to the Programming Problems section. Although it is borderline Combinatorics, the heart of the problem lies in analysis of divisibility, so I placed it in the Number Theory forum. By the way, what a challenging puzzle idea with a su...
by euler
Mon Mar 27, 2006 5:06 pm
Forum: News, Suggestions, and FAQ
Topic: How Do I... Post Fixed Width Text?
Replies: 0
Views: 7967

How Do I... Post Fixed Width Text?

(Note that spaces need to be removed from BBCode tags to make them work. If in doubt click "Quote" and look at the code I used.) Fixed width tags are useful as they allow text to appear exactly as you wish. Normally extra spaces are stripped away, but in fixed width text everyting is preserved. This...
by euler
Mon Mar 27, 2006 4:43 pm
Forum: News, Suggestions, and FAQ
Topic: How Do I... Hide Text?
Replies: 2
Views: 11310

How Do I... Hide Text?

(Note that spaces need to be removed from BBCode tags to make them work. If in doubt click "Quote" and look at the code I used.) Hiding text can be especially useful when you wish to post your solution to a problem and don't wish to influence the thinking of other members; a member needs to make a c...