Paddy

I have had two or three, but none since the shutdown - very little cause to use cash.

As you all know I am new to these and not very good, but I would say F76 - Obverse 7 reverse I. Now someone tell me I am wrong! 🙂

... One of each. On the first run through if any student can see four stamps the same colour they would know immediately that their own must both be the opposite colour. So each must be seeing at least one student with opposite colour stamps. On the second run, the first student cannot be sure if his stamps are the same colour yet, so cannot answer. By the second student the only possibility remaining is that his stamps are opposite colours, otherwise the first student would have had the answer. (I think!)

There are 10 sorts of people in the world: those that understand Binary numbers, and those that don't.

Thanks for that - brilliantly comprehensive but concise response! PS - I have been meaning to get a copy of ESC for ages and have now ordered one from Amazon.

I am involved in a conversation on another forum about Gothic florin varieties and the books I have (Spink and the Coin Yearbook) seem a bit short on detail. Another poster as said: "It claims that on 1853, 1856 no dot after the date is very rare and that on 1858,1859 no dot after date is merely rare, 1865 and 1866 can have a colon after the date and it lists various date overs and an extra t in brit: and differring numbers of arc on some years." I am bemused because all the 1856 florins listed on Ebay are without dot, so I wonder if the reference he has got it wrong. The other variations are listed except the colon after date - which I know exist because I have one from 1865 at the moment. Has anyone out there got the necessary up to date references to put me right, or can point to an online resource for it?

Interesting - MDCDX, although it works is not a valid Roman numeral. Correct notation would be MCMX. See https://www.numere-romane.ro/convert-roman-numerals-to-arabic-numbers.php for an explanation. Put simply, it is invalid to have a "subtractive group", in this case CD, following a letter for an amount in the same range, in this case D.

Another old one: A man is travelling with his dog, a rabbit and a large cabbage. He comes to a river and can only cross by the small boat tied up there. Unfortunately he can only fit one of his items in the boat with him, and he cannot leave the dog with the rabbit, or the rabbit with cabbage unattended at any time. How does he get across?

That's another "Groan"!

I like the fact that the sixpence is "defiantly silver", which the George IV crown certainly isn't!

With no one volunteering a solution I decided to see if the answer was online anywhere - and it is. Here is a comprehensive solution on wikipedia along with several further problems and solutions on the same theme: https://en.wikipedia.org/wiki/Goat_problem I didn't know it was quite THAT complicated!

Comes up as a download - do you have a link instead?

Sorry if I confused you - the orientation of the ring is irrelevant. Sorry!

OK - here is a serious challenge for a mathematician. It has been bugging me for years and I don't know the solution: You have a perfectly circular field and a goat. You tether it to a fixed point on the edge of the field - how long does the chain need to be so that it can eat precisely half the area of the field? (You can ignore the reach of the goats neck.)

Your pictures are far more elegant than my words! I couldn't be bothered taking all those photos!

You beat me to listing a similar one! 1. Q moves 2 squares straight down 2. diagonal 4 squares up and right 3. left sideways 4 squares to be above original starting place 4. diagonal 3 squares down and right to finish in the bottom right corner of the 9 - task complete!

I warned you it was not easy! Using the dates on the coins for ref: 1. 1914 slides to above 1913 and 1912 2. 1913 slides to above 1917 and 1967 3. 1917 slides to fill the gap between 1914 and 1913. Most people, even after being shown it, start by moving 1912 (or 1917) first, and then it is impossible.

That is brilliant news - thank you for putting in so much effort on these sites, which I believe will be the master reference for the future. As posted a couple of years ago, I do have a collection of halfpennies, including quite a few varieties in the Victorian era. They could do with re-photographing, but let me know if you could use pictures of them as they are.

Just thought it might be a distraction to share any intriguing news about the Coronavirus from around the world. This article from Bangkok triggered the idea: https://www.bangkokpost.com/world/1891715/shenzhen-bans-eating-of-cats-and-dogs-after-coronavirus Seems the Chinese are finally cracking down on the wild food markets, including cats and dogs. Long overdue!

No worry about the dates - just the circle shape. I put them in so I/you can describe the moves. It is trickier than it looks - best to try with coins on a table.

Here is another old chestnut: Arrange 6 coins as per the top picture. You have 3 moves to get to the bottom picture. In each move you can slide just one coin - it must not move any other coin in sliding and must come to rest so that it is touching two or more other coins. How do you do it?

An umbrella?

That is great observation! I wonder if @secret santa would consider expanding his section on George III pennies to include these for posterity?

Isn't it something like "Everything I say is a lie"? This leaves it impossible for the Cannibal!

Yes it is. You say to whichever robot you choose: "If I were to ask the other robot which door he would say was safe, what would he answer?" Which ever you have asked you get one half truth and one half lie - making a lie overall, and so you choose the other door.