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Good morning everyone

 

Cloudy here at present but forecast to remain dry.

 

Yogi, well done on that cricket quiz - you must know more than you thought to get a perfect 10 out of 10

 

The base covering of the pavement past my house should be done this morning so there's a risk that my Viegin Media cable could get hit by the heavy roller.

 

I hope everyone has a good day

El Loro

Gargoyles on cathedrals and older churches have been around for centuries. They are stone carvings on the outside near to top and are used to channel rain water from the roof away from the walls through their mouths. 6 more gargoyles are to be installed at Gloucester cathedral representing various districts of Gloucestershire.
https://www.bbc.co.uk/news/uk-...cestershire-48459590


The ones mentioned are of a suffragette (Annie Kenney for Stroud), a rugby player for Gloucester, a horse jockey for Cheltenham) and the strangest one a cheese roller which they say represents Tewkesbury. Coopers Hill of cheese rolling fame is south east of Gloucester, south of Cheltenham. Tewkesbury is north of Gloucester and Cheltenham so a bit odd.

El Loro

Good morning everyone.

Still raining up here 

El, I think my score was down to luck - although some of the correct phrases were familiar to me, which is why I chose them as my answer.

I’m glad the Annie Kenny gargoyle will not be grotesque 

Fingers crossed that heavy roller doesn’t damage your Virgin cable

Summer, I hope you enjoyed your cake 

Have a good day, all.

Yogi19

Listening to the Infinite Monkey Cage on Radio 4 and they had this poser.

You are asked a question, you think of an answer, then you you think that may be wrong and a second answer comes to mind.
The poser is which answer is more likely to be correct, your initial thought or your second thought? This poser only relates to where you do have a second thought.

 

It seems that the second thought is more likely to be correct than the first thought,

El Loro

And now a puzzle for you.

What number is next in the sequence of numbers?
11
101
191

 

If you answer 281 that would be correct. That's the more straightfoward answer - just add 90 each time.

 

However if you answered 821 that would also be correct. However that is considerably harder. It's to do with prime numbers. For anyone who hasn't stopped reading they are what are called prime quadruplets. That's because 11,13,17 and 19 are prime numbers, as are 101,103,107 and 109 ; 191,193,197 and 199; and 821,823,827 and 829. As numbers which end in 5 are divisble by 5 it's impossible for 15,105,195 or 825 to be prime numbers so those have to be ignored.

El Loro
El Loro posted:

And now a puzzle for you.

What number is next in the sequence of numbers?
11
101
191

 

If you answer 281 that would be correct. That's the more straightfoward answer - just add 90 each time.

 

However if you answered 821 that would also be correct. However that is considerably harder. It's to do with prime numbers. For anyone who hasn't stopped reading they are what are called prime quadruplets. That's because 11,13,17 and 19 are prime numbers, as are 101,103,107 and 109 ; 191,193,197 and 199; and 821,823,827 and 829. As numbers which end in 5 are divisble by 5 it's impossible for 15,105,195 or 825 to be prime numbers so those have to be ignored.

I got 281 

 

prime quadruplets are beyond me 

Yogi19
 Yogi19 posted:
El Loro posted:

By the way, if you want to know how prime numbers have their uses, one major way is encryption. This article attempts to explain it in relatively simple terms:
https://www.abc.net.au/news/sc...yption-works/9338876

Did you say that explained it in simple terms?! 

I did say relatively simple terms
Here's a more complex article:
https ://en.wikipedia.org/wiki/RSA_(cryptosystem) (this forum doesn't work for some Wiki articles because of the syntax used - you would need to copy that address into your browser bar and remove the space I've put after https to be able to get to the article).
Here's just one sentence from it:
"Compute Îŧ(n), where Îŧ is Carmichael's totient function. Since n = pq, Îŧ(n) = lcm(Îŧ(p),Îŧ(q)), and since p and q are prime, Îŧ(p) = φ(p) = p − 1 and likewise Îŧ(q) = q − 1. Hence Îŧ(n) = lcm(p − 1, q − 1)"

El Loro
Last edited by El Loro
El Loro posted:
 Yogi19 posted:
El Loro posted:

By the way, if you want to know how prime numbers have their uses, one major way is encryption. This article attempts to explain it in relatively simple terms:
https://www.abc.net.au/news/sc...yption-works/9338876

Did you say that explained it in simple terms?! 

I did say relatively simple terms
Here's a more complex article:
https ://en.wikipedia.org/wiki/RSA_(cryptosystem) (this forum doesn't work for some Wiki articles because of the syntax used - you would need to copy that address into your browser bar and remove the space I've put after https to be able to get to the article).
Here's just one sentence from it:
"Compute Îŧ(n), where Îŧ is Carmichael's totient function. Since n = pq, Îŧ(n) = lcm(Îŧ(p),Îŧ(q)), and since p and q are prime, Îŧ(p) = φ(p) = p − 1 and likewise Îŧ(q) = q − 1. Hence Îŧ(n) = lcm(p − 1, q − 1)"

 Consider me well and truly baffled 

Yogi19
El Loro posted:

Gargoyles on cathedrals and older churches have been around for centuries. They are stone carvings on the outside near to top and are used to channel rain water from the roof away from the walls through their mouths. 6 more gargoyles are to be installed at Gloucester cathedral representing various districts of Gloucestershire.
https://www.bbc.co.uk/news/uk-...cestershire-48459590


The ones mentioned are of a suffragette (Annie Kenney for Stroud), a rugby player for Gloucester, a horse jockey for Cheltenham) and the strangest one a cheese roller which they say represents Tewkesbury. Coopers Hill of cheese rolling fame is south east of Gloucester, south of Cheltenham. Tewkesbury is north of Gloucester and Cheltenham so a bit odd.

love cathedrals and Gargoyles EL but in a more traditional way

Rocking Ros Rose
Yogi19 posted:
El Loro posted:

By the way, if you want to know how prime numbers have their uses, one major way is encryption. This article attempts to explain it in relatively simple terms:
https://www.abc.net.au/news/sc...yption-works/9338876

Did you say that explained it in simple terms?! 

agree yogi

Yogi19 posted:
El Loro posted:
 Yogi19 posted:
El Loro posted:

By the way, if you want to know how prime numbers have their uses, one major way is encryption. This article attempts to explain it in relatively simple terms:
https://www.abc.net.au/news/sc...yption-works/9338876

Did you say that explained it in simple terms?! 

I did say relatively simple terms
Here's a more complex article:
https ://en.wikipedia.org/wiki/RSA_(cryptosystem) (this forum doesn't work for some Wiki articles because of the syntax used - you would need to copy that address into your browser bar and remove the space I've put after https to be able to get to the article).
Here's just one sentence from it:
"Compute Îŧ(n), where Îŧ is Carmichael's totient function. Since n = pq, Îŧ(n) = lcm(Îŧ(p),Îŧ(q)), and since p and q are prime, Îŧ(p) = φ(p) = p − 1 and likewise Îŧ(q) = q − 1. Hence Îŧ(n) = lcm(p − 1, q − 1)"

 Consider me well and truly baffled 

same here

equate prime numbers to binary numbers (0,1) - computer language  don't know why  

Rocking Ros Rose

Ros, on the subject of prime numbers and binary numbers there's no direct connection for all primes as such though binary numbers have been used by computers when trying to see if a number is prime or not.

 

As I mentioned, that's for primes generally but there is a subset where there is a direct connection with binary numbers and that's Mersenne primes. A Mersenne prime number is a prime number of the format 2 to the power of a number (n) less 1. For instance for n = 3, 2 to the power of 3 = 8 less 1 = 7 which is a prime number. If n = 7 , the result is 127 which is also prime. If you understand binary numbers you will realise that all Mersenne primes consist of 1s in binary, 127 in binary is 1111111 for instance.
Mersenne numbers are directly connected with perfect numbers. Such a perfect number is of the format 2n-1(2n - 1), If n is 7 the result is 8128. If you were to list all the numbers which are its proper divisors (including 1) and add then up you'd get 8128. Such a perfect number in binary will always start with a series of 1s and then a series of 0s. 8128 in binary is 1111111000000.

El Loro

At present the highest known prime number, a Mersenne prime, is 282,589,933 − 1. So in binary that's 82,589,933 1s.

 

It's not known if there's a finite number of Mersenne primes. There is an infinite number of prime numbers. That's easy to prove - if you were to multiple every prime number known (ignoring 2) together and deduct 1 or 2 (doesn't matter which) you would get a number which cannot be divided by any of those numbers so it has to be either a prime number or a multiple of prime numbers not known.

El Loro

As mentioned above a perfect number is one where the sum of its proper divisors is itself. For instance the proper divisors of 28 are 1,2,4,7 and 14 and the sum of those is 28.

 

There are also amicable numbers, that's 2 numbers where the sum of the propert divisors of one number is the other and vice versa. The lowest amicable numbers are 220 and 284.
Proper divisors of 220 are 1,2,4,5,10,11,20,22,44,55 and 110 which total 284,
Proper divisors of 284 are 1,2,4,71 and 142 which total 220.

 

Perfect numbers and amicable numbers are types of sociable numbers where the sum of the proper divisors of a number leads to a number where the sum of the proper divisors leads to a number and cycles on until you get back to the original number. In the case of perfecr numbers, the length of the cycle is just the 1 number and for amicable numbers just the 2 numbers. There are longer cycles, the longest one known consists of 28 numbers and starts with 14316.

 

There are also friendly numbers which are different to the above though,

El Loro
El Loro posted:

Good morning everyone

 

Sunny and a warm day here. Squiggle, I thnk the weather for the southerm half of the country is expected to be hot in places particularly in the east - I think it's just for today though.

 

Ros, like you I find the idea of modern gargoyles a bit odd

 

I hope everyone has a good day

didn't like the modern gargoyles TBH EL

Rocking Ros Rose
El Loro posted:

Ros, as an addendum to the above, n is always a prime number itself but not all prime numbers used for n result in a Mersenne prime - very few do.

 

Also, as far as I know it's still unproven that there are no odd perfect numbers (using a different format to Mersenne primes) though none has been found,

love these posts EL - you obviously have  a very astute mathematical brain well above me

Rocking Ros Rose
Last edited by Rocking Ros Rose

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