Category Archives: Fun Math Facts

A MATHCOUNTS Problem with Multiple Answers 🙂

Posted on August 19, 2024 by kevin

The following is MATHCOUNTS 2012 National Competition Sprint Round Problem 22: In circle $O$, shown, $OP=2$ units, $PL=8$ units, $PK=9$ units and $NK=18$ units. Points $K$, $P$ and $M$ are collinear, as are points $L$, $P$, $O$ and $N$. What … Continue reading →

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Elon Musk’s Interview Question

Posted on July 27, 2021 by kevin

It is known that Telsa/SpaceX CEO Elon Musk would ask a job candidate some brain teaser questions during an interview, such as the following: You’re standing on the surface of the earth. You walk one mile south, one mile west, … Continue reading →

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Circles in a Square – Part 11

Posted on January 11, 2020 by kevin

8 semi-circles are drawn along the side lines inside of a unit square as shown in the following figure, with another circle centered at the center of the square and tangent to all of 8 semi-circles. What is the area of … Continue reading →

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Solution to November 23, 2019′s Challenge

Posted on November 23, 2019 by kevin

According to Pythagoras theorem, the length of the street is $13$ blocks. However, if you look at the following diagram, Bob actually walks 16 street blocks 🙂

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Solution to November 21, 2019’s Challenge

Posted on November 22, 2019 by kevin

Actually, you can not make such a shape in our 3-dimension world 🙂 You need to be living in a 4-dimension universe to construct $10$ equilateral triangles with only $10$ matchsticks. The 4-dimension object is called tetrahedral pyramid or 5-Cell. … Continue reading →