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You have two bags of similar (weight, texture) solid pills. One bag contains red pills and the other contains green pills. There are 13 pills in one bag and 14 pills in the other. Today, tomorrow, and the day after tomorrow you must select and consume a valid pill set from the following options:

  • [3 green pills and 8 red pill]
  • [3 green pills and 4 red pill]
  • [4 green pills and 3 red pill]

Although you are blind, your colorblind friend is there to assist you. Neither of you know which bag contains which colored pills.

Side effects (Upon you):

  • When you take an invalid pill set you die.

Side effects (Upon your friend):

  • Concurrently taking 3 red pills today will instantly blind your friend forever.

    • Consecutively taking 2 red pills today will instantly blind your friend for 24 hours.

      • Taking 1 red pill today will instantly remove a positive memory from your friend for 48 hours.

  • Concurrently taking 3 green pills today will instantly fix your friend’s color blindness forever.

    • Consecutively taking 2 green pills today will temporarily fix your friend’s color blindness, tomorrow.

      • Taking 1 green pill today will temporarily fix your friend’s color blindness, the day after tomorrow.

  • Taking any number of green pill within a minute after taking any number of red pills will instantly undo the red pill’s side effects. Green pill side effects will still apply.

  • Taking any number of red pill within a minute after taking any number of green pills will instantly undo the green pill’s side effects. Red pill side effects will still apply.

How can you insure the cure of your friend’s colorblindness indefinitely and your survival?

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    $\begingroup$ I suppose my guide dog can't help much... $\endgroup$
    – Will
    Commented Jan 28, 2016 at 16:25
  • $\begingroup$ Can our friend notice the loss of a positive memory, allowing him to figure out that the pill he just took was red? Alternatively can we tell him a joke, have him take a pill, then ask if he remembers the joke to test for pill colour? $\endgroup$
    – Ninety-Three
    Commented Jan 28, 2016 at 16:39
  • $\begingroup$ You're dead either way, since you need 15 red pills and no bag has more than 14. $\endgroup$
    – JonTheMon
    Commented Jan 28, 2016 at 16:57
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    $\begingroup$ @JonTheMon Nothing says you have to use all the pillsets. I just assumed you can use any of the three on a given day $\endgroup$
    – StephenTG
    Commented Jan 28, 2016 at 16:59
  • $\begingroup$ @Ninety-Three Your friend can't notice a loss of a positive memory. Also you don't know what thought will be removed. $\endgroup$
    – MG22
    Commented Jan 28, 2016 at 17:00

1 Answer 1

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Denote the bags as A and B, where A has 14 pills and B has 13. Have your friend grab two pills from A, and hold three from B in his other hand (so he knows where it is if he goes blind). Your friend takes the two from A, and determines if he's gone blind or not:

If he's blind, he takes the pills he grabbed from B. B is green, A is Red. Once the green pill he took fixes his vision, have him label the bags (leave them in distinct places so he doesn't mix them up). There are now 12 red pills and 10 green ones, so you can take 4 red and 3 green each day and everything is good

If he isn't blind, he should take 1 more from A (or 3 if taking 2 then 1 green doesn't work), and put the three pills from B back. Have him label the bags (A is green, B is red), and you'll have at least 9 green and 13 red left. Take 4 red and 3 green each day, and it'll all be dandy

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  • $\begingroup$ @Raystafarian Why? $\endgroup$
    – StephenTG
    Commented Jan 28, 2016 at 16:56
  • $\begingroup$ @Raystafarian I'm only ever taking one of the allowed pillsets $\endgroup$
    – StephenTG
    Commented Jan 28, 2016 at 16:58
  • $\begingroup$ Ah, I added a condition when I read it. My bad! $\endgroup$
    – Raystafarian
    Commented Jan 28, 2016 at 16:58
  • $\begingroup$ Having your friend Randomly take 2 pills from a random bag will not work. I will elaborate once answer is posted. $\endgroup$
    – MG22
    Commented Jan 28, 2016 at 17:34
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    $\begingroup$ Oh, I see. For some reason I assumed that you taking a pill would have the effect listed on your friend. $\endgroup$
    – StephenTG
    Commented Jan 28, 2016 at 18:19

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