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  1. Math

    Sliding-Coin Puzzles

    Geometric arrangements of coins can serve as the basis for all sorts of puzzles. One popular variant involves going from one configuration to another by sliding coins, subject to given constraints, and doing so in the fewest possible moves. Rearrange the rhombus into a circle using three moves. Turn the triangle upside-down in three moves. […]

    By Ivars Peterson
  2. Animals

    Better Than Real: Males prefer flower’s scent to female wasp’s

    In an extreme case of sex fakery, an orchid produces oddball chemicals to mimic a female wasp's allure so well that males prefer the flower scent to the real thing.

    By Susan Milius

  3. 19209

    Your article says that “lactose, a sugar in milk, commonly elicits allergic reactions.”