We know from the Fun Fact Seven Shuffles that 7 random riffle shuffles are enough to make almost every configuration equally likely...
Continue reading...algebra
Quick Square Roots
Here’s a very quick way to generate the square root of N. Let A0=N. Then generate a sequence of numbers A1, A2,...
Continue reading...Mug Trick
Take a mug that has a handle, and fill it with coffee. Hold the mug in your hand. Now, without...
Continue reading...Chords of a Unit Circle
Take N equidistant points on the unit circle. Pick one of those points, then draw chords from it to all...
Continue reading...Behold! the Pythagorean Theorem
Figure 1 shows one of the simplest proofs of the Pythagorean Theorem. It is also perhaps the earliest recorded proof, known...
Continue reading...Squaring Numbers between 40 and 60
Here’s a quick way to square numbers between 40 and 60. You know the squares of 40, 50, and 60,...
Continue reading...Multiplying Complementary Pairs
Quick! What’s 23 x 27? 621 There’s a trick to doing this quickly. Can you see a pattern in these...
Continue reading...Visual Multiplication with Lines
Here’s a way to multiply numbers visually! Suppose you want to multiply 22 by 13. Draw 2 lines slanted upward...
Continue reading...Complex Roots Made Visible
Everyone learns that the roots of a polynomial have a graphical interpretation: they’re the places where the function crosses the x-axis. But...
Continue reading...Mind-Reading Number Trick
Think of a number, any positive integer (but keep it small so you can do computations in your head). 1....
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