Options

Can you solve this maths problem?

24

Comments

  • Options
    TrollHunterTrollHunter Posts: 12,496
    Forum Member
    ✭✭
    That's what I think.

    High-5!!
  • Options
    marlmanmarlman Posts: 661
    Forum Member
    ✭✭
    Me and my two flat mates walk past a shop and see a second hand TV on sale for £15 we all put £5 in and go in and buy it.

    The shop owner comes after us and says sorry the TV was only £10 and gives us £5 back.

    We all have £1 back so we all spent £4 each which is £12 plus the £2 which is left is £14

    Where is the other £1?
  • Options
    chaffchaff Posts: 985
    Forum Member
    ✭✭
    marlman wrote: »
    Me and my two flat mates walk past a shop and see a second hand TV on sale for £15 we all put £5 in and go in and buy it.

    The shop owner comes after us and says sorry the TV was only £10 and gives us £5 back.

    We all have £1 back so we all spent £4 each which is £12 plus the £2 which is left is £14

    Where is the other £1?

    Apparently you and your two flatmates can't work out how to share £5 between you.
  • Options
    Chris FrostChris Frost Posts: 11,022
    Forum Member
    ✭✭
    The real answer is
    Bernie and Al thought Cheryl was just being an annoying bint so the boys left her and went for a beer. Later that night they met Mandy and Lisa. The night went significantly better for the boys after that.
  • Options
    Chris FrostChris Frost Posts: 11,022
    Forum Member
    ✭✭
    marlman wrote: »
    Me and my two flat mates walk past a shop and see a second hand TV on sale for £15 we all put £5 in and go in and buy it.

    The shop owner comes after us and says sorry the TV was only £10 and gives us £5 back.

    We all have £1 back so we all spent £4 each which is £12 plus the £2 which is left is £14

    Where is the other £1?

    You're only worried about £1!!

    Where's the other £2 gone? The telly was a tenner, not £12. So you've lost £3 in total. Remind me never to split a restaurant bill with you lot.
  • Options
    jsmith99jsmith99 Posts: 20,382
    Forum Member
    ✭✭✭
    6, 16, 20, 26, 46 and 66 - which is the odd one out?

    6 - it's the only one which is a product of two consecutive primes

    16 - the only square

    20 - only one not of the form 10x + 6 (ok, 2(5x + 3) for the pedants).

    26 - only one which is a multiple of 13

    46 - err ... ditto for 23

    66 - not a lottery number.
  • Options
    EvieJEvieJ Posts: 6,039
    Forum Member
    jsmith99 wrote: »
    6 - it's the only one which is a product of two consecutive primes

    16 - the only square

    20 - only one not of the form 10x + 6 (ok, 2(5x + 3) for the pedants).

    26 - only one which is a multiple of 13

    46 - err ... ditto for 23

    66 - not a lottery number.

    By jove I think you've got it!! :D
  • Options
    TerraCanisTerraCanis Posts: 14,099
    Forum Member
    ✭✭
    I go to dinner with Alice, Bob, and Cheryl. We look at the menu. Just as I've decided what I want, but before we've had time to discuss our preferences, the waiter comes over and asks whether we're all ready to order.

    After a short pause, we simultaneously give the same answer, which is either "Yes", "No", or "I don't know". But which?
  • Options
    Victim Of FateVictim Of Fate Posts: 5,157
    Forum Member
    jsmith99 wrote: »
    6 - it's the only one which is a product of two consecutive primes

    16 - the only square

    20 - only one not of the form 10x + 6 (ok, 2(5x + 3) for the pedants).

    26 - only one which is a multiple of 13

    46 - err ... ditto for 23

    66 - not a lottery number.

    Where x is an integer.
  • Options
    Ethel_FredEthel_Fred Posts: 34,127
    Forum Member
    ✭✭✭
    It's not maths, it's logic. You don't need to understand maths to get the right answer.
  • Options
    snoweyowlsnoweyowl Posts: 1,922
    Forum Member
    ✭✭✭
    deleted
  • Options
    exlordlucanexlordlucan Posts: 35,375
    Forum Member
    16, that one doesn't come with rice included.
    Spot on :)
  • Options
    bart4858bart4858 Posts: 11,436
    Forum Member
    ✭✭
    jsmith99 wrote: »
    20 - only one not of the form 10x + 6 (ok, 2(5x + 3) for the pedants).

    In other words, the only one that doesn't end in 6!

    (I thought it might be 46 because the others can all be turned upside-down on a 7-segment display and still form numbers. 46 forms '9h')
  • Options
    bart4858bart4858 Posts: 11,436
    Forum Member
    ✭✭
    TerraCanis wrote: »
    I go to dinner with Alice, Bob, and Cheryl. We look at the menu. Just as I've decided what I want, but before we've had time to discuss our preferences, the waiter comes over and asks whether we're all ready to order.

    After a short pause, we simultaneously give the same answer, which is either "Yes", "No", or "I don't know". But which?

    Are you all responding individually or on behalf of everyone else?

    If individually, then presumably it's "Yes" because you'd be saying "Yes", and you've told us the others gave the same answer.

    Otherwise it could be "I don't know". Or is that pause significant?
  • Options
    Victim Of FateVictim Of Fate Posts: 5,157
    Forum Member
    TerraCanis wrote: »
    I go to dinner with Alice, Bob, and Cheryl. We look at the menu. Just as I've decided what I want, but before we've had time to discuss our preferences, the waiter comes over and asks whether we're all ready to order.

    After a short pause, we simultaneously give the same answer, which is either "Yes", "No", or "I don't know". But which?

    Assuming that you're all telling the truth, then it's "I don't know" because the question was whether you were all ready to order, and none of you knows whether the other two are ready.

    Reminds me of when I was little and we were going on a class trip and I didn't have a pencil, and the teacher asked "Has everyone picked up a pencil?" I said "no", but was drowned out by the rest of the class calling out "yes". Then I got in trouble for not having a pencil. Damn, that was a buried memory...
  • Options
    JurassicMarkJurassicMark Posts: 12,877
    Forum Member
    ✭✭
    Assuming that you're all telling the truth, then it's "I don't know" because the question was whether you were all ready to order, and none of you knows whether the other two are ready.

    I agree.
    Reminds me of when I was little and we were going on a class trip and I didn't have a pencil, and the teacher asked "Has everyone picked up a pencil?" I said "no", but was drowned out by the rest of the class calling out "yes". Then I got in trouble for not having a pencil. Damn, that was a buried memory...

    Although you forgot to bring a pencil, at least you were the only one who correctly answered the teacher's question.
  • Options
    droogiefretdroogiefret Posts: 24,117
    Forum Member
    ✭✭✭
    deleted

    I get it !
  • Options
    wychwych Posts: 854
    Forum Member
    ✭✭
    TerraCanis wrote: »
    I go to dinner with Alice, Bob, and Cheryl. We look at the menu. Just as I've decided what I want, but before we've had time to discuss our preferences, the waiter comes over and asks whether we're all ready to order.

    After a short pause, we simultaneously give the same answer, which is either "Yes", "No", or "I don't know". But which?

    Assuming that the "short" pause was long enough to allow anyone to say "No" who hadn't yet decided what he/she wanted, the answer is presumably "Yes".

    Everyone reasons similarly, thus. "The question was whether or not we are all ready to order. Therefore, any one of the other 3 who hasn't yet decided what he/she wants could & surely would have said "No" immediately, because he/she would know that must be the correct answer. However, even after this short pause none of the other 3 has in fact said "No", therefore all 3 of them must have already decided what they want. Since I too already know what I want, we must all be ready to order & the correct answer must therefore be "Yes"."
  • Options
    JurassicMarkJurassicMark Posts: 12,877
    Forum Member
    ✭✭
    wych wrote: »
    Assuming that the "short" pause was long enough to allow anyone to say "No" who hadn't yet decided what he/she wanted, the answer is presumably "Yes".

    Everyone reasons similarly, thus. "The question was whether or not we are all ready to order. Therefore, any one of the other 3 who hasn't yet decided what he/she wants could & surely would have said "No" immediately, because he/she would know that must be the correct answer. However, even after this short pause none of the other 3 has in fact said "No", therefore all 3 of them must all have already decided what they want. Since I too already know what I want, we must all be ready to order & the correct answer must therefore be "Yes"."

    Think the 'short pause' thing may be a red herring, but the only logical answer is "I don't know" regardless.

    Anyone saying 'No" immediately would have been the wrong thing to do, as none of them knew whether the other two had decided or not. You cannot assume anything during this short pause.
  • Options
    droogiefretdroogiefret Posts: 24,117
    Forum Member
    ✭✭✭
    Think the 'short pause' thing may be a red herring, but the only logical answer is "I don't know" regardless.

    Anyone saying 'No" immediately would have been the wrong thing to do, as none of them knew whether the other two had decided or not. You cannot assume anything during this short pause.

    I think you are right. Even if they all knew what they wanted when the waiter asked, they clearly weren't ready to order .... because they didn't.

    But after the pause 'No' is the wrong response, because the pause has taken place and who knows if they are now ready to order? They are clearly ready to speak.

    Knowing what you want and being ready to order are two different things. One requires a willingness to speak - the other doesn't.
    :D
  • Options
    JurassicMarkJurassicMark Posts: 12,877
    Forum Member
    ✭✭
    I think you are right. Even if they all knew what they wanted when the waiter asked, they clearly weren't ready to order .... because they didn't.

    But after the pause 'No' is the wrong response, because the pause has taken place and who knows if they are now ready to order? They are clearly ready to speak.

    Knowing what you want and being ready to order are two different things. One requires a willingness to speak - the other doesn't.
    :D

    Although you agree with my conclusion, I'm not certain you fully understand the logic behind it.

    The important word in this logic question is in bold: the waiter comes over and asks whether we're ALL ready to order.

    The three people know individually whether they are ready or not, but as they don't know whether the other two are ready or not, the only correct answer they can give is "I don't know". No individual had enough information to say "Yes" or "No" on behalf of the group, it's as simple as that.

    It doesn't matter if there was no pause, a short pause, or a long pause, as long as there was no communication between them, there is only one correct answer. I believe the short pause is the time it took for them to logically consider the correct answer.

    If you already knew all of that, then I apologise. :)
  • Options
    TerraCanisTerraCanis Posts: 14,099
    Forum Member
    ✭✭
    wych wrote: »
    Assuming that the "short" pause was long enough to allow anyone to say "No" who hadn't yet decided what he/she wanted, the answer is presumably "Yes".

    Everyone reasons similarly, thus. "The question was whether or not we are all ready to order. Therefore, any one of the other 3 who hasn't yet decided what he/she wants could & surely would have said "No" immediately, because he/she would know that must be the correct answer. However, even after this short pause none of the other 3 has in fact said "No", therefore all 3 of them must have already decided what they want. Since I too already know what I want, we must all be ready to order & the correct answer must therefore be "Yes"."

    That's it exactly.

    In some variants the other diners answer "I don't know" sequentially so that it's the fourth person who knows the answer to the waiter's question exactly as posed.
    Knowing what you want and being ready to order are two different things. One requires a willingness to speak - the other doesn't.
    :D

    Fair enough, but remember that this takes place in the world of mathematical / logical puzzles, in which a man fills a bath with two gallons of water per minute and one gallon of water per minute runs down the plughole - and it never occurs to him to put the plug in!
  • Options
    bri160356bri160356 Posts: 5,147
    Forum Member
    TerraCanis wrote: »
    That's it exactly.

    In some variants the other diners answer "I don't know" sequentially so that it's the fourth person who knows the answer to the waiter's question exactly as posed.



    Fair enough, but remember that this takes place in the world of mathematical / logical puzzles, in which a man fills a bath with two gallons of water per minute and one gallon of water per minute runs down the plughole - and it never occurs to him to put the plug in!

    .......probably too pissed after his night out in your bleedin’ restaurant ! ;-)
  • Options
    JurassicMarkJurassicMark Posts: 12,877
    Forum Member
    ✭✭
    wych wrote: »
    Assuming that the "short" pause was long enough to allow anyone to say "No" who hadn't yet decided what he/she wanted, the answer is presumably "Yes".

    Everyone reasons similarly, thus. "The question was whether or not we are all ready to order. Therefore, any one of the other 3 who hasn't yet decided what he/she wants could & surely would have said "No" immediately, because he/she would know that must be the correct answer. However, even after this short pause none of the other 3 has in fact said "No", therefore all 3 of them must have already decided what they want. Since I too already know what I want, we must all be ready to order & the correct answer must therefore be "Yes"."
    Think the 'short pause' thing may be a red herring, but the only logical answer is "I don't know" regardless.

    Anyone saying 'No" immediately would have been the wrong thing to do, as none of them knew whether the other two had decided or not. You cannot assume anything during this short pause.

    After the question poser said that your solution is correct, just re-checked it and realised that I was wrong. Didn't click that "No" would be a correct answer for the group if anyone of them was not ready to order. I feel embarrassed now. :blush:
    I think you are right....

    No I wasn't, ignore my explanations.
  • Options
    hunter23hunter23 Posts: 3,097
    Forum Member
    ✭✭✭
    why don't she just tell them when it is? then it wouldn't be a problem
Sign In or Register to comment.