A blog post from 2009 created a social networking storm when it was re-posted on Twitter recently, and has now been re-tweeted thousands of times.

The tweet claimed that an elementary school student had been taught that ‘9÷0＝0’. This has caused outrage among netizens, who have offered novel explanations as to why this answer is incorrect.

**From Infoseek News:**

## ‘9÷0＝0’?: ‘Just a minute’ For the Problem That Was Given To Students in An Elementary School

It’s a bit out of the blue but question: ‘What is 9 ÷ 0?’. Did you know that there are several answers to this?

…I don’t suppose anyone inadvertently answered ‘zero’, though. The real answer is ‘It can’t be divided’ or ‘There is no answer’. At least, within the bounds of the arithmetic and math that is taught at elementary and middle school, the answer is taken to be that ‘you shouldn’t divide things by zero’, and of course to say that the answer is ‘zero’ is a mistake. However, the claim on Twitter that ‘There is a school that teaches that 9 ÷ 0= 0?!’ has become a talking point.

It all started with a photograph uploaded on the blog ‘Supebito Pics’. The blogger’s son, who was in the third year of elementary school, had his homework corrected, and the blogger found that it had been corrected to read ‘9÷0＝0’. By the way, according to the answer booklet, the correct answer was ‘0’. Even seems that even Supebito Pics stopped himself from marking it as correct.

The blog post itself was written in 2009, but when someone tweeted the post, saying ‘How could this kind of thing happen?’ it spread immediately. Various comments were exchanged, such as ‘Is there really an elementary school that teaches 9÷0＝0?! We’re all doing the problem (even in my house). We’re confused,’ and it became a huge blogstorm. The thread of tweets was even collated on the Twitter trend site Togetter.com, where it has gained a huge influence already having over 170,000 views and over 4,000 re-tweets.

It is unclear as to whether it was simply that the question was a bad one, or perhaps the issue was the standing of the school, but at any rate, the fact that ‘you shouldn’t divide things by zero’ is a mathematical convention. If there happen to be people around you who learned that 9÷0＝0, then please, gently correct them.

*Initially I wrote that ‘In mathematics you mustn’t divide by zero’, but it was pointed out to me that in high school mathematics, there are occasions when things are treated as being divided by zero, and therefore I changed the expression.

**Comments from 2ch.net:**

名無しさん＠１３周年：

Divide by zero ERROR

名無しさん＠１３周年:

On the iPhone calculator, if you try ●÷0 then it comes up in huge letters saying ERROR w

名無しさん＠１３周年：

To say that you shouldn’t divide by zero, I mean, what are you supposed to do if you divide by zero? Accidents happen when you’re told not to do things. What then, huh?

名無しさん＠１３周年：

A lot of elementary school teachers are second or third generation graduates from third-rate universities.

名無しさん＠１３周年：

When my son’s friend said that pi was 3.14 in the classroom, he came under a barrage of fire from his classmates who said ‘Liar!! It’s 3!’, and now he cries because he’s getting bullied and called ‘3.14’.

名無しさん＠１３周年：

9sinθ÷cosθ＝9tanθ

9sin(π/2)÷cos(π/2)＝9tan(π/2)

9÷0＝9tan(π/2)

名無しさん＠１３周年：

For example, even if you can divide 1,000,000 yen evenly between five people, you can’t divide it by zero people. It’s not that there’s no answer to this, it’s that there’s never been a model for it.

名無しさん＠１３周年：

I asked ten kids who are in the first year of middle school. Eight of them answered ‘0’. They told me they’d learned it in when they were in elementary school. I don’t know they really learned it there though.

名無しさん＠１３周年：

Fail w

This problem itself is one of the fundamentals of mathematics. Mathematics is a completely different kind of scholarship to physics and chemistry.

名無しさん＠１３周年：

Those of you who are trying to force calculus and infinity and functions onto a question for kids in the early years of elementary school can just shut up. Or maybe just give an explanation that an elementary school student can understand.

ココ電球 _/::o-ν ◆tIS/.aX84. ：

There are loads of idiots who only ever graduated from elementary school about. They don’t even understand mathematical limits. For those guys who say that you shouldn’t divide by zero, I’ll show you algebraic infinity. Are you stupid?

名無しさん＠１３周年：

You guys still talking about this? w. Let’s just think of the generation that have kids as children themselves. Things spread quickly from one child to their friends, and then the whole school, but it seems like when they asked the teacher the answer carried over w

名無しさん＠１３周年：

This is a division problem that was given to kids in the third year of elementary schoolw. It’s not a problem that was given to high school students, nor was it a problem given to physicists, chemists, or mathematicians.

名無しさん＠１３周年：

It’s the same with division, but I just don’t get how 9 x 0= 0. I can only ever think of it as if you multiply 9 by 0, then you just have the 9 you started with…

名無しさん＠１３周年：

There’s nothing for it but to ask an Indian.

名無しさん＠１３周年：

This thread is frightening www

名無しさん＠１３周年：

When the teacher said that 9÷0=0, then maybe they meant ‘There’s no answer～’?

名無しさん＠１３周年：

We learned that it was impossible or indefinite.

名無しさん＠１３周年：

To Mr. Poorly Educated who said that 9÷0=∞ : Zero points(^-^)/ The correct answer is that it’s almost infinity; it’s close to absolute infinity, but it’s not infinite, it’s finite m9(^Д^)ﾌﾟｷﾞｬｰ

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