Eli5 why is a number divided by zero undefined?

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Example I have a pizza I cut it into zero pieces shouldnt it be still one whole pizza?
Since I didn’t cut it so it’s still whole

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Anonymous 0 Comments

But it isn’t zero pieces, it’s 1 piece: the whole pizza.

There are many different ways of looking at what division is. One way is to look at it like repeated subtraction (in the same way multiplication is treated as repeated addition).

Let’s say we want to use the pizza to represent dividing 600 by 200. And let’s say, coincidentally, the pizza weighs 600 grams. So you subtract 200 grams but cutting off a 200 gram slice. That’s 1. There are 400 grams left. So you cut off another 200 gram slice. That’s 2. And now there are 200 grams left which you subtract for 3. 600 divided by 200 is 3.

Now let’s try that with 0. We want to divide 600 by 0. So we subtract 0 by cutting off 0 grams. There are 600 grams left. That’s 1. We subtract 0 from the remaining 600 grams leaving 600 grams behind. That’s 2. We subtract 0 from the remaining 600 grams leaving 600 grams behind. That’s 3. We subtract 0 from the remaining 600 grams leaving 600 grams behind. That’s 4. We subtract 0 from the remaining 600 grams leaving 600 grams behind. That’s 5.

I hope you can see where this is going.

From a more “pure” mathematical sense, when we say “A divided by B equals C” we are also, at the same time, saying that “B times C equals A.” So when B is 0, it messes up with that second part because anything times 0 is zero. Which either means nothing B could be would, when multiplied by 0, equal A (when A isn’t already 0), or *anything* B could be would, when multiplied by 9, equal A (when A is 0). Hence, *undefined.*

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