Martin Gardner (1914 – 2010) was an American popular mathematics and popular science writer, with interests also encompassing scientific skepticism, micromagic, philosophy, religion, and literature—especially the writings of Lewis Carroll, L. Frank Baum, and G. K. Chesterton.
With 12 matches you can easily create a shape with area 9 and a shape with area 5, as shown on the picture below. Can you rearrange the 12 matchsticks, so that they encompass an area of 4?
Remark: You should have only one resulting shape and no matches should be unused.
Two identical bolts are placed together so their grooves intermesh. If you move the bolts around each other as you would twiddle your thumbs, holding each bolt firmly by the head so it does not rotate and twiddling them in the direction shown below, will the heads:
(a) move inward
(b) move outward, or
(c) remain the same distance from each other?
You are in a room with nothing else but two indistinguishable iron rods. You know that one of them is magnetized, how can you figure out which one?
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