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A Problem For 8 Year Olds

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Okay. This one has quite a few of us stumped but it was part of a homework assignment for an 8 year old.

The problem is formatted as three circles in a line, each divided into thirds and oriented like a radiation sign (i.e. an upper left third, an upper right third and a lower central third, which I shall denote a,b, and c respectively and represent as a triple (a,b,c). Each third has a number in it, except position c in the last circle.

These things are usually solved by either realising some simple mathematical relationship, a visual trick or a combination of both.

For example (4,6,42) (9,6,45) (2,7, ?) (The answer being 41. To get this multiply a by b and swap the digits)

or: (4,3,24) (7,2,28) (3,8,?) (The answer is 48. c=2*a*b )

So here is the problem which we cannot solve...well we can get solutions but none of them match up with the alleged numerical solution: (3,9,23) (4,5,30) (6,7,?)

The obvious solution to me is a*b+c=50, hence the answer would be 8...but the answer is (allegedly) 24. Any idea?

Edited to fix misprint c->b noted by DTMark

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I have been looking at it for ten minutes and I really have no idea.

Other than to say that the answers to these things pretty well have to be unambiguous, and I therefore wonder if the given answer is a misprint.

I can get to two more possible answers and these sorts of problems should probably only have one answer.

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I'm thinking you are correct DTM. The formula giving 8 seems reasonable for an 8 year old to come up with. Given that, even if there was a simple solution giving 24, it would still be competing with a*b+c=50.

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I'm thinking you are correct DTM. The formula giving 8 seems reasonable for an 8 year old to come up with. Given that, even if there was a simple solution giving 24, it would still be competing with a*b+c=50.

Working backwards - if the last answer is 24 and the sum of the two digits is 13 then you need to add 11.

If you take the first one of the thee this also works. Add 3 and 9 to get 12 then add another 11 gets you 23.

It's the middle one that fails this. Unless it's misprinted and the "30" should in fact be "20".

Then you can get your 24 and it works. It might even be unambiguous, haven't tested.

My inclination remains that your methodology is right and the given answer is wrong. Or the question is wrong.

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Okay. This one has quite a few of us stumped but it was part of a homework assignment for an 8 year old.

The problem is formatted as three circles in a line, each divided into thirds and oriented like a radiation sign (i.e. an upper left third, an upper right third and a lower central third, which I shall denote a,b, and c respectively and represent as a triple (a,b,c). Each third has a number in it, except position c in the last circle.

These things are usually solved by either realising some simple mathematical relationship, a visual trick or a combination of both.

For example (4,6,42) (9,6,45) (2,7, ?) (The answer being 41. To get this multiply a by b and swap the digits)

or: (4,3,24) (7,2,28) (3,8,?) (The answer is 48. c=2*a*b )

So here is the problem which we cannot solve...well we can get solutions but none of them match up with the alleged numerical solution: (3,9,23) (4,5,30) (6,7,?)

The obvious solution to me is a*b+c=50, hence the answer would be 8...but the answer is (allegedly) 24. Any idea?

Edited to fix misprint c->b noted by DTMark

Surely this isn't a question for 8 year olds :unsure:

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Okay. This one has quite a few of us stumped but it was part of a homework assignment for an 8 year old.

The problem is formatted as three circles in a line, each divided into thirds and oriented like a radiation sign (i.e. an upper left third, an upper right third and a lower central third, which I shall denote a,b, and c respectively and represent as a triple (a,b,c). Each third has a number in it, except position c in the last circle.

These things are usually solved by either realising some simple mathematical relationship, a visual trick or a combination of both.

For example (4,6,42) (9,6,45) (2,7, ?) (The answer being 41. To get this multiply a by b and swap the digits)

or: (4,3,24) (7,2,28) (3,8,?) (The answer is 48. c=2*a*b )

So here is the problem which we cannot solve...well we can get solutions but none of them match up with the alleged numerical solution: (3,9,23) (4,5,30) (6,7,?)

The obvious solution to me is a*b+c=50, hence the answer would be 8...but the answer is (allegedly) 24. Any idea?

Edited to fix misprint c->b noted by DTMark

yes Winston, its 24....dont you see?

there is no misprint in circle 2.

(a+1)*(b-1)=c( digits reversed)

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This is not a maths problem, it is a cryptic crossword type puzzle. It's not for 8 year old school students, its for middle age socially disfunctional loners.

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This is not a maths problem, it is a cryptic crossword type puzzle. It's not for 8 year old school students, its for middle age socially disfunctional loners.

That's probably why I spent too much time thinking about it! :huh:

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That would imply that circle 2 was "5*4 = 02" :blink:

clearly, you need to another day in room 101

cant you see it already says 02?

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Homework for an 8 year old, eh?

It looks more like a book cypher to me.

The name of the book will cost you half the gold.

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Homework for an 8 year old, eh?

It looks more like a book cypher to me.

The name of the book will cost you half the gold.

Probably if an 8 year gets it right within moments loads of black helicopters will swoop and men in black suits will carry the youngest off never to be seen again.

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Probably if an 8 year gets it right within moments loads of black helicopters will swoop and men in black suits will carry the youngest off never to be seen again.

Only if he makes the phone call...

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Working backwards - if the last answer is 24 and the sum of the two digits is 13 then you need to add 11.

If you take the first one of the thee this also works. Add 3 and 9 to get 12 then add another 11 gets you 23.

It's the middle one that fails this. Unless it's misprinted and the "30" should in fact be "20".

Then you can get your 24 and it works. It might even be unambiguous, haven't tested.

My inclination remains that your methodology is right and the given answer is wrong. Or the question is wrong.

Yep, funnily enough after my last post we also came up with the 30 should be 20 hypothesis; it is an easy typo to make and it makes the problem more suitable for an 8 year old. Whatever the case, something is amiss.

Anyhow, it appears that between HPC and facebook we aren't missing something obvious. Thanks for taking the time to think about the problem.

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Your next assignment gentlemen:

Find all positive integers a, b such that sqrt(a) + sqrt(B) = sqrt(2009).

(Obviously no software allowed - in fact, no calculators either.)

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its for middle age socially disfunctional loners.

DTMark might not be too pleased about this description... ;)

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DTMark might not be too pleased about this description... ;)

When I was writing about some of the other local attractions in our area viz. the meet-up, I wondered if people might be interested in, say, clubs or something lively to do if they're coming a long way.

Then I realised there aren't any round here anyway. The nearest is about 15 miles away. So their omission wasn't down to me being a mildly ********, sad old git with a narrow range of interests, though as I read that description back the ring of truth it has to it brings some discomfort.

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  • 244 Brexit, House prices and Summer 2020

    1. 1. Including the effects Brexit, where do you think average UK house prices will be relative to now in June 2020?


      • down 5% +
      • down 2.5%
      • Even
      • up 2.5%
      • up 5%



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