Author Archives: kevin

Problem of the Day – November 26, 2019

Posted on November 26, 2019 by kevin

How many 4-digit numbers are there with digits in absolute descending order, such as 8520? And how many 4-digit numbers are there with digits in absolute ascending order, such as 3569?

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Solution to November 25, 2019′s Challenge

Posted on November 26, 2019 by kevin

By connecting various points in the figure, we have the following: It is obvious that the radius of each quarter circle is $\dfrac{\sqrt{2}}{2}$, and the area of two green regions is: $$\dfrac{1}{2}-\dfrac{1}{4}\cdot\pi\cdot(\dfrac{\sqrt{2}}{2})^2=\dfrac{1}{2}-\dfrac{\pi}{8}$$ Therefore, the total area of the blue regions … Continue reading →

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Problem of the Day – November 25, 2019

Posted on November 25, 2019 by kevin

In the following figures, 4 quarter circles join at the center of a unit square. Find the area of the shaded regions in blue.

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Problem of the Day – November 24, 2019

Posted on November 24, 2019 by kevin

In the following figure, a semi-circle is inscribed with maximum size inside a unit square. Find the radius of the the semi-circle. 

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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 🙂

Posted in Daily Problems, Fun Math Facts, Geometry | Comments Off on Solution to November 23, 2019′s Challenge