explain xkcd - User contributions [en]

2348: Boat Puzzle

2026-04-15T23:33:16Z

2603:6011:1F0:2A40:650C:3BE2:A94D:49B6: /* Explanation */

{{comic
| number = 2348
| date = August 19, 2020
| title = Boat Puzzle
| image = boat_puzzle.png
| titletext = 'No, my cabbage moths have already started laying eggs in them! Send the trolley into the river!' 'No, the sailing wolf will steal the boat to rescue them!'
}}

==Explanation==
This comic is a twist on {{w|Wolf, goat and cabbage problem|an old riddle}}. In the original riddle, a person has to cross a river in a boat that can only hold them and one other object. They have a wolf, a goat, and a cabbage that they need to bring across with them, similar to the first panel. If the wolf is left alone with the goat, however, the wolf will eat the goat; and if the goat and cabbage are alone, the goat will eat the cabbage. (The problem can be solved in seven trips.) There are other variations of this problem, using different animals and foods, such as the fox-chicken-corn variation.

However, the comic quickly devolves into surrealism in the later panels as new characters show up, bringing deviations of the original "cabbage", "goat", and "wolf" that add extra layers of complexity to the riddle. [[White Hat]] brings extra wolves and cabbages. [[Black Hat]], in his traditional [[72:_Classhole|classhole]] style, brings {{w|cabbage moth}}s which will infest unsupervised cabbages with destructive larvae, and boat-destroying {{w|termite}}s. How he intends to bring them across the river (or even if he wants to) is unknown, but it brings to mind the parable of {{w|The Scorpion and the Frog}}, where the scorpion stings (out of instinct) the frog ferrying it across the river. [[Beret Guy]] arrives with a wolf who can operate a boat, who could perhaps serve as a second pilot to expedite the crossing, so long as he is not asked to ferry a goat, and also a goat who eats wolves, possibly in addition to the cabbages. This is unusual,{{cn}} as one would expect from Beret Guy's associates.

The last panel is a reference to the {{w|Trolley_Problem|Trolley Problem}}, a moral test that asks the participant whether they would passively let people in the way of an uncontrollable trolley die or actively divert the trolley to kill a single person standing on a branch of the tracks. The comic gives a twist here too: according to the title text, the characters must choose between stopping the trolley full of wolves with a cushion of cabbages (in which Black Hat's cabbage moths have laid eggs, which he implicitly argues are morally equivalent to "innocent children") or letting it crash into the river (at which point the wolf who can operate a boat will steal the boat to rescue the wolves from the trolley, which will delay the other characters from crossing the river). The cushion of cabbages is also most likely a reference to the {{w|Avatar: The Last Airbender}} gag "my cabbages" in which a cabbage vendor routinely has his cart full of cabbages destroyed as a running joke.

The River Crossing puzzle was also mentioned in [[1134: Logic Boat]] and referenced in [[589: Designated Drivers]] and [[2684: Road Space Comparison]].

The Trolley Problem was also mentioned in [[1455: Trolley Problem]] and referenced in [[1938: Meltdown and Spectre]].

==Solving the problem==

Unlike typical Logic Boat problems the presence of multiple humans makes finding a solution almost trivial, however trying to determine the solution with the least number of trips could still make the somewhat challenging. Because the set of constraints are both ambiguous and incomplete, it requires the reader to make assumptions that, in turn, will lead to different solutions.

===Reasonable Assumptions===

The following assumptions can be made based on the setup of the problem or are necessary to avoid an unsolvable puzzle.

* '''Cueball is an observer.''' He is set up as an observer there to solve the problem, not pilot the boat or "watch" the cargo.
* '''The boat can only hold two items.''' This is standard in logic boat problems. Groups of insects count as one item.
* '''Black Hat and Beret Guy both want to cross the river with their cargo'''. Neither states that they wish to cross the river like Ponytail and White Hat, but it can be inferred from the setup of the scenario.
* '''The termites will destroy the boat ''after'' crossing.''' Otherwise the problem is unsolvable. This is similar to the {{w|Poncelet–Steiner theorem}}, which shows that any compass-and-straightedge construction can be completed with a "rusty compass", so long as the compass works at least once.
* '''The wolf-eating goat also eats cabbage.''' The wolf-eating constraint adds to the goat's existing constraints.
* '''The sailing wolf follows the command of an adjacent human.''' The alternatives require more assumptions for a solvable puzzle.
* '''The sailing wolf returns the trolley wolves to the near shore.''' The trolley wolves show no indication of wanting to cross the river.
* '''Stopping the trolley destroys all the cabbages.''' Otherwise the event does not affect the logic puzzle.
* '''The pack of wolves from the trolley will eat a human or wolf-eating goat left by themselves.''' Aligns with the spirit of the constraints.
** '''A wolf can protect a human from a pack of wolves'''. A human who is accompanied by one of the wolves who want to cross the river should not count as being "alone" for the purpose of getting eaten by the wolves from the trolley; otherwise, there is no way to get everyone across.

===The Trolley===

The trolley problem creates two versions of the puzzle, one where the cabbages are destroyed, the other where they are not and a wolf rescue takes place. The ethical issues associated with the trolley problem are independent from the logic of how to cross the river.

===Solutions===

* General

With four humans involved, the first trip across can bring an extra human who then can guard the cargo as it is brought across in arbitrary order with care being taken not to have predator and prey alone together at the end. The termites must be last cargo ferried across as they will destroy the boat.

* The Trolley is Stopped

The cabbages are destroyed. The second to last trip brings across the last human and the last trip brings across the termites.

* The Trolley is not Stopped

A pack of wolves is now on the near bank. The last human is brought across in the third to last trip, followed by the last wolf and lastly the termites.

===Missing Information===

No information is provided about whether or not the humans all get along with each other and this is left as a possible exercise for the reader given all of the characters' varying personality traits. However the sailing wolf would likely come in handy if certain humans (ex Black Hat, Beret Guy) cannot be left alone. It is also probable that certain characters might not serve in the capacity as a cargo guard.

It is also unclear if humans can leave with their cargo once all the cargo has been brought across. This could complicate matters if a far side "guard" leaves early.

==Transcript==
:[Cueball and Ponytail are standing on the bank of a river. There is a boat in the river. A goat and wolf are also on the riverbank, and Ponytail is holding a cabbage.]
:Ponytail: I need to cross the river. I have a wolf, a goat, and a cabbage.
:Cueball: Hmm.

:[White Hat appears, accompanied by two wolves and pulling a wagon full of cabbages.]
:Cueball: OK, here's what-
:White Hat: Hi, I also need to cross. I have two wolves and 100 cabbages.

:[Black Hat arrives, surrounded by a cloud of flying creatures and carrying a jar of bugs under his arm. Beret Guy follows with another wolf and goat on leashes.]
:Black Hat: I have 50 cabbage moths and 2,000 boat-destroying termites.
:Beret Guy: I have a wolf that can operate a boat, and a goat that eats wolves.

:[The fourth panel is a zoomed-out shot, where everything but the sky appears black.]

:[A trolley speeds in, leaving a trail of dust in its wake. A person is standing on the front, and many ears are barely visible above the seats.]

:Cueball: Hang on, I need to make a spreadsheet.
:Trolley operator: Look out!
:Trolley operator: My wolf-filled trolley is out of control and can only be stopped by a cushion of cabbages!

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Black Hat]]
[[Category:Comics featuring Beret Guy]]
[[Category:Logic]]
[[Category:Animals]]
[[Category:Food]]

3232: Countdown Standard

2026-04-15T23:11:53Z

2603:6011:1F0:2A40:650C:3BE2:A94D:49B6: /* Explanation */

{{comic
| number = 3232
| date = April 13, 2026
| title = Countdown Standard
| image = countdown_standard_2x.png
| imagesize = 474x222px
| noexpand = true
| titletext = Anyone who is caught counting 'three ... two ... one ... zero ... GO!' will be punished with a lifetime of eating only ISO standard food samples.
}}

==Explanation==
{{incomplete|This page WILL BE CREATED IN TWO...THREE...ONE...ZERO...NEGATIVE ONE...NOW! Don't remove this notice too soon.}}
This comic reflects the common {{tvtropes|OnThree|trope}} of people preparing for a synchronized action as a group (such as lifting something heavy, or [[:Category:The Race|having an electric skateboard race]]) counting to get everybody to start the action at the same time, without first having agreed at what point in the count they will act. Two of the ways that people often count up can be confusing: the action can be either performed just as the speaker says 'three', or a second later ('four' if the speaker was still counting). If the people involved do not all have the same understanding, and so end up acting out of sync, which could result in undesirable outcomes, such as damage, injury, or just a dispute over the interpretation of the instruction, not the least those who might jump the gun or the speaker perhaps intending to start on '{{tvtropes|ILied|two}}'.

This comic alleges that, if [[Randall]] gained control of the {{w|International Organization for Standardization}} (ISO), he would standardize counting to go ''down'' from three and have the 'go'-point be at zero. However, this proposal would be no better than counting up, as some people may expect to act on the 'one' or, as the title text suggests, to have a 'zero' before the 'go!', leading to exactly the same problems. Moreover, most people are unlikely to refer to the ISO before starting a countdown, and this is likely to simply lead to the problem outlined in [[927: Standards]].

"Deprecated" is a term applied to something that is no longer recommended for use, so you should fix things so as not to use it anymore. It is commonly used when a standard is replaced by a newer version or an alternative approach, but may still be in use in legacy applications. In this case, it is hard to imagine where there would be a situation where a need to maintain a deprecated standard would arise, since such countdowns tend to be short-lived affairs, so any starting before the publication of the new standard would be unlikely to continue running for appreciable periods after it.

The fact that these are called "countdowns", yet the ones being complained about are counts that go ''up'', is probably intentional, and cause for additional irritation among those who are bothered by the inherent inconsistencies.

The ISO is an international organization that is responsible for standardizing many things (such as technology and safety standards) to allow for smooth interoperability between countries, manufacturers, and so on. However, it doesn't standardize everyday actions like countdowns. Other standards organizations that have somewhat similar functions include the [https://www.nist.gov/ National Institute of Standards and Technology] (NIST) and the [https://www.ansi.org/ American National Standards Institute] (ANSI), which are technically American but have considerable international influence.{{acn}}

The title text refers to "ISO standard food samples". The ISO doesn't offer such samples, but does have documents which describe how food samples should be prepared for standardized analysis. For example, [https://www.iso.org/standard/29628.html ISO 16050:2003] documents how "cereals, nuts and derived products" are to be analyzed for aflatoxins. If your punishment were to repeatedly test cereals and nuts for toxins, that would probably be quite unpleasant, especially if one of your bowls happened to contain said toxins. {{w|ISO 3103}} describes a standardized method for {{What If|71|brewing tea}}. It's unclear why such samples would be considered particularly unpleasant or inappropriate for consumption. Perhaps they would be assumed to be unimaginably bland because they would be 'lowest common denominator' illustrations of the base definition of each food. There ''are'' NIST Standard Reference Materials for food, such as [https://shop.nist.gov/ccrz__ProductDetails?sku=2387 peanut butter] and "[https://shop.nist.gov/ccrz__ProductDetails?sku=1548b typical diet]". Hacker lore describes a supposed [http://www.catb.org/jargon/html/A/ANSI-standard-pizza.html "ANSI-standard pizza"].

Apparently eating these food samples is, in Randall's opinion, suitable punishment for doing “3, 2, 1, 0, Go!” for a countdown. In this he is likely to be disappointed, as he will discover that punishment for non-compliance with standards is not within the remit of the ISO. The possibility of including 0 in such a countdown would be an example of an off-by-one error, as described in [[3062: Off By One]].

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
:[The comic shows three different ways of counting down]

:One ... Two ... '''''Three!''''' [red X, followed by red text] Deprecated
:One ... Two ... Three ... '''''Go!''''' [red X, followed by red text] Deprecated
:[These first two both followed by a red curly bracket followed by red text:] Too easy to mix up

:Three ... Two ... One ... '''''Go!''''' [green tickmark, followed by green text] ISO Standard

:[Caption below the comic:]
:If I were in charge of ISO, the first thing I'd do would be to standardize the way people count out loud before doing something in sync.

{{comic discussion}}<noinclude>
[[Category:Comics with color]]

3232: Countdown Standard

2026-04-15T23:10:25Z

2603:6011:1F0:2A40:650C:3BE2:A94D:49B6: /* Explanation */

{{comic
| number = 3232
| date = April 13, 2026
| title = Countdown Standard
| image = countdown_standard_2x.png
| imagesize = 474x222px
| noexpand = true
| titletext = Anyone who is caught counting 'three ... two ... one ... zero ... GO!' will be punished with a lifetime of eating only ISO standard food samples.
}}

==Explanation==
{{incomplete|This page WILL BE CREATED IN TWO...THREE...ONE...ZERO...NEGATIVE ONE...NOW! Don't remove this notice too soon.}}
This comic reflects the common {{tvtropes|OnThree|trope}} of people preparing for a synchronized action as a group (such as lifting something heavy, or [[:Category:The Race|having an electric skateboard race]]) counting to get everybody to start the action at the same time, without first having agreed at what point in the count they will act. Two of the ways that people often count up can be confusing: the action can be either performed just as the speaker says 'three', or a second later ('four' if the speaker was still counting). If the people involved do not all have the same understanding, and so end up acting out of sync, which could result in undesirable outcomes, such as damage, injury, or just a dispute over the interpretation of the instruction, not the least those who might jump the gun or the speaker perhaps intending to start on '{{tvtropes|ILied|two}}'.

This comic alleges that, if [[Randall]] gained control of the {{w|International Organization for Standardization}} (ISO), he would standardize counting to go ''down'' from three and have the 'go'-point be at zero. However, this proposal would be no better than counting up, as some people may expect to act on the 'one' or, as the title text suggests, to have a 'zero' before the 'go!', leading to exactly the same problems. Moreover, most people are unlikely to refer to the ISO before starting a countdown, and this is likely to simply lead to the problem outlined in [[927: Standards]].

"Deprecated" is a term applied to something that is no longer recommended for use, so you should fix things so as not to use it anymore. It is commonly used when a standard is replaced by a newer version or an alternative approach, but may still be in use in legacy applications. In this case, it is hard to imagine where there would be a situation where a need to maintain a deprecated standard would arise, since such countdowns tend to be short-lived affairs, so any starting before the publication of the new standard would be unlikely to continue running for appreciable periods after it.

The fact that these are called "countdowns", yet the ones being complained about are counts that go ''up'', is probably intentional, and cause for additional irritation among those who are bothered by the inherent inconsistencies.

The ISO is an international organization that is responsible for standardizing many things (such as technology and safety standards) to allow for smooth interoperability between countries, manufacturers, and so on. However, it doesn't standardize everyday actions like countdowns. Other standards organizations that have somewhat similar functions include the [https://www.nist.gov/ National Institute of Standards and Technology] (NIST) and the [https://www.ansi.org/ American National Standards Institute] (ANSI), which are technically American but have considerable international influence.{{acn}}

The title text refers to "ISO standard food samples". The ISO doesn't offer such samples, but does have documents which describe how food samples should be prepared for standardized analysis. For example, [https://www.iso.org/standard/29628.html ISO 16050:2003] documents how "cereals, nuts and derived products" are to be analyzed for aflatoxins. If your punishment were to repeatedly test cereals and nuts for toxins, that would probably be quite unpleasant, especially if one of your bowls happened to contain said toxins. {{w|ISO 3103}} describes a standardized method for {{What-If|71|brewing tea}}. It's unclear why such samples would be considered particularly unpleasant or inappropriate for consumption. Perhaps they would be assumed to be unimaginably bland because they would be 'lowest common denominator' illustrations of the base definition of each food. There ''are'' NIST Standard Reference Materials for food, such as [https://shop.nist.gov/ccrz__ProductDetails?sku=2387 peanut butter] and "[https://shop.nist.gov/ccrz__ProductDetails?sku=1548b typical diet]". Hacker lore describes a supposed [http://www.catb.org/jargon/html/A/ANSI-standard-pizza.html "ANSI-standard pizza"].

Apparently eating these food samples is, in Randall's opinion, suitable punishment for doing “3, 2, 1, 0, Go!” for a countdown. In this he is likely to be disappointed, as he will discover that punishment for non-compliance with standards is not within the remit of the ISO. The possibility of including 0 in such a countdown would be an example of an off-by-one error, as described in [[3062: Off By One]].

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
:[The comic shows three different ways of counting down]

:One ... Two ... '''''Three!''''' [red X, followed by red text] Deprecated
:One ... Two ... Three ... '''''Go!''''' [red X, followed by red text] Deprecated
:[These first two both followed by a red curly bracket followed by red text:] Too easy to mix up

:Three ... Two ... One ... '''''Go!''''' [green tickmark, followed by green text] ISO Standard

:[Caption below the comic:]
:If I were in charge of ISO, the first thing I'd do would be to standardize the way people count out loud before doing something in sync.

{{comic discussion}}<noinclude>
[[Category:Comics with color]]

3232: Countdown Standard

2026-04-13T23:38:08Z

2603:6011:1F0:2A40:650C:3BE2:A94D:49B6: /* Explanation */