Archive for the ‘math’ Category

Pick an Alien – A Math Problrm at a Chinese Elementary School

January 22, 2013


The above is a math question for a Chinese elementary school. See if you can solve it. Characters in the first row are aliens and the second row non-aliens. Pick up the alien from the third row.

A little math question for junior rocket funs

August 26, 2012

The figure above shows a rocket taking off vertically. When the rocket reaches a height of 12 kilometers, the angles of elevation from points A and B on level ground are 84.1o and 62.7o, respectively. What is the distance between points A and B?


An Example of Plane geometry in China

May 25, 2012

How to avoid careless mathematical errors?

April 22, 2011

I found this discussion on reddit “How to avoid careless mathematical errors?“:

Hi //math.

I am a high school student who happens to be VERY good at math, but who consistently fails to get As on tests due to careless errors. Most of the time, they come from forgetting a 0 after a decimal place, multiplying instead of dividing, putting a decimal point in the wrong place, or just factoring wrong. I actually had to drop a Precalc Honors class because I got Ds on tests from the sheer number of stupid mistakes I made, despite understanding the material very well.

I assume that this occurs because I work quickly, but if I work slowly, I run out of time on the test. Additionally, my handwriting is horrible, but there’s really nothing I can do about that. And even when I check my answers after finishing, I still miss my mistakes.

I know that this issue is going kill my college GPA, so I want to fix it as soon as I possibly can. What do you guys do to avoid stupid mistakes?

I read through the comments and found some really good ones:


A geometry problem for Chinese elementary school students

April 15, 2011

Given the area of a (blue) regular hexagon to be 2009. Find the area of the (red) hexagon. Here each green line segment connects one vertex to the mid-point of the adjacent side in clockwise direction. The red small hexagon is formed by those six green line segments. Here is a hint:


A math question in Beijing elementary school entrance exam

March 17, 2011

I’ve seen this question before. A Ph.D. student Wu Baojun (吴宝俊) of Chinese Academy of Science claimed that no one in his office could solve the problem. This time, it is brought up to media during the 2011 NPC & CPPCC sessions. So, let me translate it to English:

Given nine digits 1 through 9. You will be asked to separate them into different categories. For example, 1, 3, 5, 7, 9; and 2, 4, 6, 8 are separated by odd and even numbers. Now here are three categories: 1, 3, 7, 8; 5, 9; and 2, 4, 6. How are they separated?


To All Math Geeks Who Are Single

August 16, 2010

Source: Matrix67

A Chinese Elementary School Entry Exam Question

June 30, 2010

The following is said to be a question in the entry exam of an elementary school in Beijing.

Given nine integers 1 through 9, we can groups them as follows:

1, 3, 5, 7, 9
2, 4, 6, 8


Yes, there are other ways to avoid a math problem

November 8, 2009

I read with interest a letter to AW&ST titled “Avoiding a math problem” by George Epstein, Lost Angeles, California. The letter is copied as follows:


LaTex in WordPress blog

September 8, 2009

I haven’t used TeX/LaTeX since I left from academic world more than ten years ago. This becomes a problem sometimes after I start blogging. When I have to write mathematical expressions, I have to end to using either existing images (e.g.Normal distribution function, RSS — root sum square) or simple HTML (e.g. 24th Chinese Mathematical Olympiad, 24th Chinese Mathematical Olympiad (continued)).But recently I found that I might be able to use it again. The news comes from Ben Lorica’s blog that WordPress has enabled LaTeX. So, I’d like to try it with the interesting pictures from the following found functions.

The function is \frac{1}{3}(x^3+y^3) = 6xy

As you’ve noticed, the expression is actually given already. I don’t really need to write it out. Again, this is just an experiment with WP LaTeX. The web page found functions provides more examples.

For help, see LaTeX section.