As a riddle, the answer is zero legs on the bus since the bus has wheels instead of legs.

But as a maths problem; It's not a tricked question -- just a straightforward maths problem

Confirmed answer is 10990 legs.

§ Let's say the whole situation simply :

- There are 7 girls.

- Each girl has 7 backpack

- Each backpack has 7 big cats

- Each big cat has 7 little small cats.

§ Question: How many legs are there in the bus?

§ Let's focus on each part of the question systematically, write down on a piece of paper if you have to, following my steps of chains.

1. Focus on the first girl first:

A B C D E F G

Girl A has 7 backpacks

2. Now focus on first backpack A1 :

A1 A2 A3 A4 A5 A6 A7

Backpack A1 has 7 big cats

3. Now focus on first big cat :

1 2 3 4 5 6 7

Ø Each big cats have 7 small cats (that's the end of the focus)

Systematically, 7 small cats has 28 legs (7 * 4) combined with the big cat that owns this 7 small cats.

Let's call this the "cat chain", so cat chain 1has 32 legs altogether.

Ø So since there are 7 big cats

7 * 32 = 224 legs

Ø Therefore each backpack has 224 legs

Ø Finally, each girl has 7 * 224 = 1568 legs.

Lastly, since there are 7 girls, A to G, there are 7 * 1568 legs (per girl) = 10976 legs.

Now, since each girl also has 2 legs each;

SO, (7 * 2) + 10976 = 10990 legs altogether

Note: Disregarding bus driver, buses and etc…Only focus on the girl and their backpacks!

There are 7*7 = 49 bags and there are 7 + 7*7 = 56 cats in each bag, meaning there are 56*4 = 224 legs in each bag. So including the 7 children that have 2 legs each, there are 7*2 + 49(224) = 10990 legs in total.

What You Would Do

Scream, pray, worry, or wince for the coming impact (which is almost inevitable).

What You Should Do

Look for a tree to grab, or a ledge that might interrupt your fall. If you think you might land in water, rather than on rock, angle your body to enter feet first. Otherwise, go limp and don't try to stop when you hit. This could cause more injuries. Always have another competent adult with you when you are in rocky surroundings, and ideally a way (such as a satellite phone) to immediately call for help. One or more of a climbing party should have professional first aid training.

What A Science Student Might Do

Calculate the velocity of the moment right before you hit the ground given that the distance of the cliff to the ground is x, the initial velocity is zero, and the acceleration of gravity is 9.8 m/sec2.

On the lighter side

Always carry a small bunny with you, so it can blow on your face.

There are many stories of people who have been saved by a hare's breath.

You might want to see if you have any wings with you (chicken wings, buffalo wings, any kind of wings) and attach them to your back. This will likely not help.

If you're Dean Potter simply pull the cord on your base jumping pack and land safely on the ground.

Why it is a paradox

It is contradictory. If we say the statement is true, then this statement would have to be false since it was true. If we say it the statement is false, it will make the statement itself true, as that is false.

Example in Popular Culture

The liar's paradox can be found in an episode of Star Trek where Captain Kirk defeats a "superior" computer by introducing a logic loop similar to the question's liar paradox. (Kirk: "Everything Mudd says is a lie." Harry Mudd : "I am lying.")

Language

In semantics there is the issue of truth condition, where the meaning of a sentence is conveyed if the truth conditions for the sentence are understood. A truth condition is what makes for the truth of a statement in an inductive definition of truth. The semantic theory of truth was developed from the work of a Polish logician named Alfred Tarski who attempted to formulate a new theory of truth in order to solve the liars paradox. In doing so, Tarski developed the indefinability theorem, similar to Godel's incompleteness theorem. The Theory that the concept of truth for the sentences of language cannot be consistently defined within that language means that such paradoxes as "This statement is false" do not reveal the truth or falsity of the sentence by the words that have been used.

Solution to the paradox

Let us consider "This statement is false." This quotation could also be read as "This, which is a statement, is false," which could by extent be read as "This is a statement and it is false." Let's call this quotation P. The statement that P is a statement will be called Q. If S, then R and S equals R; therefore, if Q, then P equals not-P (since it equals Q and not-P). Since P cannot equal not-P, we know that Q is false. Since Q is false, P is not a statement. Since P says that it is a statement, which is false, P itself is false. Note that being false does not make P a statement; all things that are statements are true or false, but it is not necessarily true that all things that are true or false are statements.

In summary: "this statement is false" is false because it says it's a statement but it isn't.

The question in philosophy and psychology is that while a tree falling "should make" sound, the existence of the sound can depend on its ability to be perceived (now or later). While physics states that a tree falling will create the vibrations we call sound, their existence as sound is only recognized when perceived (heard) and cannot be absolutely postulated unless and until this occurs. This can be extended beyond this example, as far as the metaphysical concepts of existence and perception, e.g. without someone or something there to perceive it, does the tree even exist at all?

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The philosophical and perceptual psychological background about this question:

Philosopher George Berkeley wrote A Treatise Concerning the Principles of Human Knowledge (1710). He wrote, in part, "But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park [...] and nobody by to perceive them. [...] The objects of sense exist only when they are perceived; the trees therefore are in the garden [...] no longer than while there is somebody by to perceive them."

"The objects of sense..." refers to objects or events that we perceive with the 5 senses--hearing, sight, smell, taste, touch. However, as a philosophy question, raises the issue of perception in philosophy: Does something still exist if we cannot perceive it with one of our senses. And, just what do we perceive...

For twenty-years after Berkeley's writing, philosophers took up " consideration of the emergence of meaning" (quote from Wikipedia). In 1754, William Fossett paraphrased Berkeley's writing in Fossett's writing, Natural States. However, it should be noted neither of these philosophers actually stated the quote in question ("If a tree falls in a forest and no one is around to hear it, does it make a sound").

Over 100 years later, in June 1883, a question was posed in The Chautauquan magazine, "If a tree were to fall on an island where there were no human beings would there be any sound." [Italics added].

This idea in 1700s-1800s was seminal work about the idea of perception. It has lead to a host of similarly phrased questions posed to students, first in Universities to philosophy and psychology students, and then to high school students.
The point is to generate thinking about problems of perception.

Some similarly stated questions include:

1. If a tree falls in the forest... [some people add other details here such as distance away] but no one HEARS it...does it make a sound.
2. If a leaf falls in the forest but no one is present to SEE it, does the leaf still fall, gathering with other leaves on the forest floor.
3. If you SMELL the strong fragrance of aftershave, but you see no one nearby, do you assume a man just passed by before you arrived there?
4. If you experience the distinctive TASTE of onions in a casserole but did not see anyone make or bake the food, can you be certain the cook added fresh onions to it.
5. If you put your hand into a hole in a closed box and you TOUCH something that feels cold and wet, can you assume it came from a block of ice.
6. (You can probably think of more of your own 'If'-perception questions.)

• The tree no one heard still thudded; the leaf still detached from the tree without requiring our sight; aftershave is typically associated with men, even if we missed seeing the man pass by; the food might have contained onion salt versus chopped onions; and lastly, everything that is 'cold and wet' is not ice.
• Likewise, Blacks and women endured years of oppression... Events halfway around the world, like wars, take place even if we don't see the fighting.... Nazis killed millions of Jews in the Holocaust... Babies and children still die of starvation in some countries... etc.

Below, other contributors take up various positions, including strictly scientific points of view.

Related Response to the above:
This is a philosophy question. Yes, events happen even though we are not paying attention. This is speaking straight logic. However, it may just depend on the individual's concept of reality.


A Question About Evidence
How do we know said tree fell if no one was around to witness it, or even hear it? It's a philosophical question, so it does puzzle the mind. It's like exercise for the mind: the more you use it the stronger it gets.


Another answer that attempts to bridge perception with science:

Although this question is often restated as a crude satire, "If Helen Keller fell over in a forest would there be any noise?", the answer stays the same. A sound does not depend on the perception by a sentient hearer. Examining the question, there are three conditions that set the scenario:

1. A tree falls - It is presumed that the tree falls through other trees branches and strikes the ground in a manner that makes satisfying "Thunk!" all of which activities generate sound waves and or vibrations. This is technically a sound or colloquially a noise.
2. in the woods - This is an ecosystem filled with receptors some definitely sentient (humans) and some of debatable levels of sentience (deer, raccoons etc.) all of which have the capacity of hearing
3. and nobody is there to hear it - Fully sentient beings, humans, are excluded but animals are not excluded.

The scenarios above would make a sound, because mum, herself, could hear her own voice. So, I do not agree with that answer and support all the perspectives above the last one. To put it simply, vibrating air is only vibrating air. That does not mean that it is making a sound, because a sound requires sensory organs and a nervous system to process the vibrations and then interpret those vibrations as sound.

Here is my analogy: If a person blows a dog whistle, does it make a sound? Not to a human, but only if there is a dog close enough to hear it.Then it would make a sound.

So the answer really should be, in my opinion: if a tree falls in the woods it does not make a sound unless there is anything from an insect to a human being to hear it. It Depends on Factors Involved It depends how hard the tree fell. What if it fell so hard that it can be heard half way around the world? Also are we assuming that the vibration in the air is not sound until it reaches our ear? What is the speed of sound? Is a ball not a ball until we catch it? Is wind not wind until we feel it? Does a chair exist to a blind individual until the individual sits in it? Sound exists whether we are around or not. It is only the matter of if anyone is around to translate the sound into information. Another Opinion I think that it does make a sound because if it makes a sound when we are there then why would it not it if we were not there?

If I knock on wood we all hear the same thing so we cannot change what it sounds like on our own (maybe small differences but barely).

So the sound is not completely in our mind; meaning that it must make a sound no matter if anyone is there or not

Really it Would
The reason it would is the same reason you don't hear much Japanese in America. Some one makes that sound and others hear it, but you don't. The answer is yes because you may not hear it and no one else will, but it will make a noise. It's the same as if you weren't near the forest but another was and a tree falls. They hear but you don't. When they tell you they heard a tree fall you believe them. That's because that person heard it but, you did not. Another Opinion Says No When the tree falls and it finally makes impact with the ground a vibration forms (in the same way ripples form when a rock is thrown into still water). This vibration sets out from all directions of the point of impact, if there is a living being within the range that the vibration can travel it will then be interpreted as a noise. If there is no living being within the distance the vibration can travel it will not be interpreted as a "noise", to be a noise it must first be experienced/perceived. So the new question is 'If a vibration is caused by something in the woods is and no one can hear or feel it is it real'? O.K. the only real answer to any metaphysical questions such as these is that consciousness makes the sound into how it will be perceived. Without consciousness the vibration could not be interpreted as a sound. Your conscious thought (the voice in your head asking this question) was the answer to the question all along. Answer Yes, it does. Sound is mechanical energy. And sound will be created when the tree falls. If no one is there to hear it, that does not negate the fact that the sound was created and radiates out from where the tree fell.

No "opinions" are needed. This is a question that is very straightforward. There is nothing rhetorical about this query, nor is there anything mysterious or metaphysical involved. The question asks about what would happen if a tree fell in the forest, and we have to assume it did to run this "thought experiment" to its conclusion. And that conclusion is that there would, indeed, be sound. It's not rocket science. According to Definition of Sound, No. According to Merriam-Webster, sound is the sensation perceived by the sense of hearing. So that means that vibrating air is just that, mechanical vibrations of air molecules. When those vibrations are perceived by the sense of hearing, then they become a sensation; the sensation of sound. That is why we have an auditory cortex in the neocortex of the brain that interprets those vibrations as a tree falling, a bird singing, or the wind whistling through the leaves.

Here is an example: If you never heard a tree fall as it crashed to the ground and you were standing in the woods blindfolded as one fell, you would hear noise. The noise would be the vibrations in the air of the tree hitting the ground. Most likely you would hear something, but you would not know what it was. But, if you had heard enough similar noises before, your brain would then be able to identify the vibrations as being produced by a tree falling. Then it would be a sound.

So, going by the Merriam-Webster definition, the tree would make air molecules vibrate, but would not make a 'sound' if it fell in the woods and nobody was there to hear it.

• The dictionary definition of hearing is "a special sensation, produced by stimulation of the auditory nerve; the stimulus (waves of sound) acting not directly on the nerve, but through the medium of the endolymph on the delicate epithelium cells, constituting the peripheral terminations of the nerve." The sound we hear is the interpretation of the stimulus we receive, which can only be made by some cognition, i.e.- Information processing which must be linked in some way with a stored memory.

• Naturally, events happen regardless of whether someone is there to witness them. Sound is a wave that forms due to an action (the friction of the air with our vocal cords produces our voice, and the collision between the tree and the ground produce the sound of the impact). So, if a tree falls it will sound, even if no one hears it it will still have had a sound. The only place where there is no sound is a vacuum, so if a tree falls in the moon then it would not sound, regardless of you being there to hear it or not.
• Even if there is no human to hear or see the tree fall, there is another creature who will hear it. A falling tree may not make a difference to us humans, but it could be a lost home to a squirrel living inside of the tree, which would hear a massive thud as the mass of wood came tumbling down to the forest floor. And now with the population of people at almost 7 billion, it is unlikely for no one to notice a tree fall. But if the tree fell in space, than no one would hear, because sound requires oxygen to resonate, so that organisms can hear it. So what if a tree falls on a planet with less oxygen, say Venus. The sound of the falling tree (depending on what distance you were listening to it from) would be less softer, and being feet from it would still require hearing aids to hear. But it doesn't matter, because the tree would just evaporate into Venus' harsh atmosphere. The noxious gas clouds would melt the tree, or the heat would burn it instantly, therefore concluding that a tree (theoretically speaking) would neither make a sound, nor exist in open space in the first place, because of the extreme temperatures and climate. Trees would only weigh more on Jupiter compared to earth, and if one was planted on their moon, it would be possible for an astronaut to carry it. And it could not fall, it would would just float around in the space time continuum, until being sucked up into a black hole vortex, eaten alive the tree would shrink to no size and infinite density. And do not forget about the civil rights of trees. Talking about them falling is like deciphering whether a person would make a sound if it fell in the forest with no one else around.
• I looked up sound in the dictionary and part of the definition was something that was heard. If no one was in the forest then it did not make a SOUND. It may have made a sound WAVE yet not a sound!
• Yes. The fact that there is no-one there that can hear it does not affect whether the falling tree makes a sound. Humans are not the only species capable of hearing anyway.
• Yes And No Because there is no one around to hear it and yes because of its greatness so it will make a huge sound but nobody will be able to hear it
• Yes because there are animals living in the forest so they will hear it. the tree will also produce sound because the sound waves will still move. [sound waves do not care if there is no one around to hear them]
• Anything that falls will of course make a noise, even if it is too soft to hear, if a tree falls in a forest it is going to hit the ground and make a noise, or if it bangs against another tree it will rustle those leaves, if you drop your remote on the carpet does it make a noise? Yes, if you drop a pencil on the ground, will it make a noise? Yes! even if no one is around to hear it it will make a noise! those molecules will still carry the noise to where they eventually fade out! So in my opinion, it will make a noise!