34
   

The worlds first riddle!

 
 
Tryagain
 
  1  
Reply Sat 6 May, 2006 07:32 am
Mark, there is a crazy guy from Utah, who says he is getting 70 calls an hour since you published his number, (and apart from the one from Shari, who he found very interesting), would like it known, that if it don't stop soon he is gonna do something about your something with a sharp pointy stick. Just thought you would like to know. Laughing


MOMRETAROURBLKE
0 Replies
 
markr
 
  1  
Reply Sat 6 May, 2006 12:03 pm
Mark in more trouble
0 Replies
 
Tryagain
 
  1  
Reply Sat 6 May, 2006 12:21 pm
Shari:

Start with a = 1, b = sqrt(2)/2, r = 1, and s = 1/2. Use as much
precision in calculation as you want in the answer. Then do these
steps:

1. A = (a+b)/2

2. B = sqrt(a*b)

3. C = (A-b)^2

4. R = 2*r

5. S = s - C*R

6. P = 2*A^2/S

7. If C = 0 to the precision used, stop, and the answer is
Pi = P to that precision.

8. Replace a by A, b by B, r by R, and s by S

9. Go back to step 1.

This is called the Brent-Salamin Algorithm. Each calculation is pretty simple, and after just a few rounds it gives answers accurate to many decimal places. (Five rounds will give 42 decimal digits, if you use that much precision.) Explaining *why* this works is very hard. Please accept that it does.

If we make our precision eight decimal places, the first few steps go
like this:

a = 1
b = 0.70710678
r = 0
s = 1/2
A = 0.85355339
B = 0.84089642
C = 0.02144661
S = 0.45710678
R = 2
P = 3.18767264
C is not small enough,

A = 0.84722490
B = 0.84720127
C = 0.00004005
S = 0.45694658
R = 3
P = 3.14168029
C is not small enough,

A = 0.84721308
B = 0.84721308
C = 0.00000000
S = 0.45694658
R = 4
P = 3.14159265
C is small enough.

Then the answer is pi = 3.14159265, to eight decimal places. Cool Cool Cool


My thanks to Shari who came up with a real neat answer to the problem that had defied logic for so long. Razz


Mark:

DAY OF THE WEEK
Sunday Cool


We rewrite the statements in the following form:

Today is Monday.
Today is Wednesday.
Today is Tuesday.
Today is either Thursday, Friday, Saturday or Sunday.
Today is Friday.
Today is Wednesday.
Today is either Saturday, Monday, Tuesday, Wednesday, Thursday or Friday.

The only day that is not mentioned twice is Sunday, so today is Sunday!


MBAARKD
barking mad Razz

FCERAYR
cry in fear Razz

STSTOENPE
stepping stone Razz


MOMRETAROURBLKE
Mark in more trouble Razz Laughing



Find a 10 digit number abcdefghij such that each digit is different, and so that the number ab is divisible by 2, abc is divisible by 3, abcd is divisible by 4, abcde is divisible by 5, abcdef is divisible by 6, abcdefg is divisible by 7, abcdefgh is divisible by 8, abcdefghi is divisible by 9, and abcdefghij is divisible by 10. Shocked Confused Question
0 Replies
 
markr
 
  1  
Reply Sat 6 May, 2006 02:29 pm
[size=8]10-DIGIT NUMBER
3816547290
[/size]
0 Replies
 
Tryagain
 
  1  
Reply Sat 6 May, 2006 03:59 pm
Amazing, simply amazing! Razz


SBOANNGTAITNLAE

YOTURRUSSETLF

CHALOILFOIRDNAIYA
0 Replies
 
markr
 
  1  
Reply Sat 6 May, 2006 08:32 pm
[size=8]banana in song title
trust in yourself
holiday in california
[/size]
0 Replies
 
markr
 
  1  
Reply Sat 6 May, 2006 08:43 pm
smeteltoumies
0 Replies
 
Tryagain
 
  1  
Reply Sun 7 May, 2006 07:19 am
Mark:

10-DIGIT NUMBER
3816547290 Cool Cool Cool

(That guy is the greatest!)




There are 10! (or 3,628,800) permutations of digits in a 10 digit number where each digit is only used once. We can use well known divisibility rules to drastically reduce the number of possibilities.

1. The even digits must be b, d, f, h, and j; and so the odds will be a, c, e, g, and i.

2. Since 5|abcde, e=5, and since 10|abcdefghij, j=0.

3. Since 4|abcd, 4|cd. Remembering that c is odd and not 5 and d is even and not 0, we have that cd=12, 16, 32, 36, 72, 76, 92 or 96. Notice that d=2 or 6.

4. Since 6|abcdef, 3|abcdef, which means that 3|(a+b+c+d+e+f). Also, 3|abc, so 3|(a+b+c). So also 3|(d+e+f). Remembering that d=2 or 6, e=5, and f is even not 0, we have def=258 or 654. Notice that f=4 or 8.

5. Since 8|abcdefgh, 8|fgh. Remembering that f=4 or 8, g is odd not 5, and h is even not 0, we have fgh=416, 432, 472, 496, 816, 832, 872, or 896. Notice that h=2 or 6.

6. Now, because we have that both d and h are either 2 or 6, none of the other even numbers can be 2 or 6. Since we already know that j=0, b=4 or 8.

7. We already observed that 3|(a+b+c). Also, a and c are odd not 5, and b=4 or 8, so we have abc=147, 183, 189, 381, 387, 741, 783, 789, 981, or 987.
From here we can find the solution by "brute force". Using the numbered items above in the order 7, 4, 5, we fill in the digits from left to right by choosing from the possibilities listed for abc, def, and fgh, making sure that no digits are repeated. Of course j is always 0, and i is chosen as the only digit that remains. We have reduced our possible digit combinations to just ten.
Of these possibilities, only one meets all of the divisibility requirements! The others work with everything except the requirement that 7|abcdefg.

a b c d e f g h I j
1 4 7 2 5 8 9 6 3 0
1 8 3 6 5 4 7 2 9 0
1 8 9 6 5 4 3 2 7 0
1 8 9 6 5 4 7 2 3 0
3 8 1 6 5 4 7 2 9 0
7 4 1 2 5 8 9 6 3 0
7 8 9 6 5 4 3 2 1 0
9 8 1 6 5 4 3 2 7 0
9 8 1 6 5 4 7 2 3 0
9 8 7 6 5 4 3 2 1 0


SBOANNGTAITNLAE
banana in song title Razz Laughing


YOTURRUSSETLF
trust in yourself Razz


CHALOILFOIRDNAIYA
holiday in California Razz


"smeteltoumies"

I can only come up with; Sometimes lute(in). Well, it does use up all the letters.



Over in Merry Olde England, two friends, Alex and Bob, go to a bookshop, together with their sons Peter and Tim. All four of them buy some books; each book costs a whole amount in shillings. When they leave the bookshop, they notice that both fathers have spent 21 shillings more than their respective sons. Moreover, each of them paid per book the same amount of shillings as books that he bought. The difference between the number of books of Alex and Peter is five.

Who is the father of Tim Question

Impossible you say? I think not!



PWROOGRREKSS


YHEOURDBEGTES
0 Replies
 
markr
 
  1  
Reply Sun 7 May, 2006 12:49 pm
[size=8]BOOKS
This is much easier than it appears. Since (x+5)^2 - x^2 doesn't equal 21 for any positive integer x, Alex can't be Peter's dad. Therefore, Alex is Tim's dad.
Alex: 5 books
Bob: 11 books
Peter: 10 books
Tim: 2 books

work in progress
hedging your bets
[/size]

smeteltoumies
0 Replies
 
Tryagain
 
  1  
Reply Mon 8 May, 2006 11:03 am
Mark:

BOOKS
This is much easier than it appears. Since (x+5)^2 - x^2 doesn't equal 21 for any positive integer x, Alex can't be Peter's dad.
Therefore, Alex is Tim's dad. Cool
Alex: 5 books Cool
Bob: 11 books Cool
Peter: 10 books Cool
Tim: 2 books Cool


For each father-son couple holds: the father bought x books of x shillings, the son bought y books of y shillings. The difference between their expenses is 21 shillings, thus x^2 - y^2 = 21.

Since x and y are whole numbers (each book costs a whole amount of shillings), there are two possible solutions: (x=5, y=2) or (x=11, y=10). Because the difference between Alex and Peter is 5 books, this means that father Alex bought 5 books and son Peter 10. This means that the other son, Tim, bought 2 books, and that his father is Alex.
Better still re-read Mark's answer.

PWROOGRREKSS
work in progress Razz

YHEOURDBEGTES
hedging your bets Razz



"Smeteltoumies"

May I safely assume you did not countenance my previous answer?
I am still on the case.




With all the numbers 0 up to 9 (using each number exactly once), can you make two fractions that add up to exactly 1 Question



A cyclist drove one kilometer, with the wind in his back, in three minutes and drove the same way back, against the wind in four minutes. If we assume that the cyclist always puts constant force on the pedals, how much time would it take him to drive one kilometer without wind Question



DSOEVFTELOWPAMREENT
0 Replies
 
markr
 
  1  
Reply Mon 8 May, 2006 06:41 pm
"May I safely assume you did not countenance my previous answer?"
You may.

[size=8]CYCLIST
12/3.5 = 3.428571... minutes

0-9
45/90 + 381/762 is one way

software development
[/size]
0 Replies
 
Tryagain
 
  1  
Reply Tue 9 May, 2006 01:21 pm
"You may." Laughing


Mark:

0-9
45/90 + 381/762 is one way Cool

There are 97 solutions to this problem, some of which can easily be calculated on the back of an envelope (such as 1/2+3548/7096), and others which are less trivial (such as 34/578+96/102).


CYCLIST
12/3.5 = 3.428571... minutes Cool

All I can say is, ?'we were close'.

The cyclist drives one kilometer in three minutes with the wind in his back, so in four minutes he drives 1 1/3 kilometer. Against the wind, he drives 1 kilometer in four minutes. If the wind helps the cyclist during four minutes and hinders the cyclist during another four minutes, then - in these eight minutes - the cyclist drives 2 1/3 kilometers. Without wind, he would also drive 2 1/3 kilometers in eight minutes and his average speed would then be 17.5 kilometers per hour. So it will take him 3 3/7 minutes to drive one kilometer.


DSOEVFTELOWPAMREENT
software development Razz


"Smeteltoumies"

I can say with a degree of confidence, that I have checked all known English permutations and come up with zilch.
Can you wait to see if anyone else can crack it?



Shari wants to expose her melons neatly for sale. Whilst doing this, she discovers that one melon is left over when she places them in groups of three. The same happens if she tries to place them in groups of 5, 7, or 9. Only when she makes groups of 11, do they fit exactly.

The Question comes to mind; Embarrassed No! Not that one, this one: How many melons does Shari have at the very least Question



(Payback time)

CPOONGUEERST
0 Replies
 
markr
 
  1  
Reply Tue 9 May, 2006 07:05 pm
hint: smeteltoumies contains a proper noun.

[size=8]MELONS
Something's wrong with my calculation. I came up with 1892, but I know damn well that Shari has exactly two very fine melons.
[/size]

pongees in court
pouer in congest
0 Replies
 
Tryagain
 
  1  
Reply Wed 10 May, 2006 11:07 am
Mark:

MELONS
Something's wrong with my calculation. Shocked (You can say that again partner) I came up with 1892, but I know damn well that Shari has exactly two very fine melons. Razz

I can well understand your lack of concentration when faced with Shari's melons. However, I do thank you for the pictorial conformation, cute!

Assume the number of melons is A. Then A-1 is divisible by 3, 5, 7 and 9. So, A-1 is a multiple of 5×7×9 = 315 (note: 9 is also a multiple of 3, so 3 must not be included!). We are looking for a value of N for which holds that 315×N +1 is divisible by 11. After some trying it turns out that the smallest N for which this holds is N = 3.

This means that Shari has at least 946 melons. (How did you come up with, exactly double this number?)

Note that for N = 14, 25, 36, etc. (so each time 11 more) it also holds that 315×N + 1 is divisible by 11.



"hint: smeteltoumies contains a proper noun." Shocked

That is so not fair. Drunk

Although I suspected as much. So did …
?'CPOONGUCEERST'

pongees in court
pouer in congest

Just to prove how difficult, if not impossible it is, the answer is:
Pogues (in) concert. (One of my favorite bands).




However, be that as it may, I wonder if you could help me as my house is on fire and I need to calculate the minimum outside surface of a cylindrical bucket with an open upper side, which can hold 30 liters of water.

What is the minimum outside surface Question

(I never said it would be easy) Laughing
0 Replies
 
markr
 
  1  
Reply Wed 10 May, 2006 12:03 pm
What's wrong with this picture:
-----------------------
(Payback time)
CPOONGUEERST

Although I suspected as much. So did …
CPOONGUCEERST
-----------------------
Are you intentionally handicapping me by withholding letters?

The proper noun in my puzzle is much more commonly known (although it does include an abbreviation).


MELONS
I guess I fixated on the number two. I solved the problem for two melons left over at each step.

[size=8]BUCKET
30L = 3000cc
r = h = 10*(3/pi)^(1/3)
Since r=h, A = 3*pi*r^2 = 913.942168 square centimeters
[/size]
0 Replies
 
Tryagain
 
  1  
Reply Wed 10 May, 2006 01:12 pm
Mark wrote;


What's wrong with this picture:
-----------------------
(Payback time)
CPOONGUEERST

Although I suspected as much. So did …
CPOONGUCEERST
-----------------------
Are you intentionally handicapping me by withholding letters? Shocked

(That is indeed a conundrum, same file, copy - paste. I suspect the ?'Management' may be removing every other ?'C'. Laughing


The proper noun in my puzzle is much more commonly known (although it does include an abbreviation).

?'I will review my non answers in light of possible new lines of enquiry'.


MELONS
I guess I fixated on the number two. Shocked I solved the problem for two melons left over at each step.

Perfectly understandable, and as they say in the news business "put that to bed" :wink:



BUCKET

(I don't think we are going to agree on that either) Sad



To whom it concerns:

May I respectfully suggest that those readers who wish to praise Mark, write direct to him and not to me - Thank you.


To Mark:

Patti (not her post name) would like you to say ?'Hi' to her. She thinks you are ?'so very clever'. Rolling Eyes

Another ?'medical case' wishes her boyfriend was like you. Rolling Eyes




What about this; You walk upwards on an escalator, with a speed of one step per second. After 50 steps you are at the end.

You turn around and run downwards with a speed of five steps per second. After 125 steps you are back at the beginning of the escalator.

How many steps do you need if the escalator stands still Question
0 Replies
 
shari6905
 
  1  
Reply Wed 10 May, 2006 01:12 pm
"MELONS
I guess I fixated on the number two. I solved the problem for two melons left over at each step. "



Hmmmm! Now I wonder WHY you would be fixated on such a number!!
0 Replies
 
Tryagain
 
  1  
Reply Wed 10 May, 2006 03:51 pm
I am sorry, all this talk of ?'Melons' leaves me perplexed. Henceforth, all references will be changed to ?'Pears' and we shall see how Mark copes with a nice pair! :wink:
0 Replies
 
markr
 
  1  
Reply Thu 11 May, 2006 02:04 am
Is Patti someone you know? How do Patti's pear of melons stack up against Shari's?
0 Replies
 
markr
 
  1  
Reply Thu 11 May, 2006 02:18 am
BUCKET (correction)
30L = 30000cc
r = h = 10*(30/pi)^(1/3)
Since r=h, A = 3*pi*r^2 = 4242.14376 square centimeters
0 Replies
 
 

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