What a great exercise it would be for a child to figure out how to “model” this wall with only equilateral triangles and squares. This is exactly the kind of thinking that the writers of the Common Core Math standards illustrate in the draft of their Geometry Progression for Grades K-6, pp. 7, 11-12. Geometiles™ were used for the modeling task, as shown above….

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## Three sisters and their PJ’s

When I saw Grace, Sophie, and Chloe in their mismatched pajamas, a question immediately popped up: if there are 3 sisters, and 3 pairs of pajamas, how many ways are there for them to wear the pajamas so that the top and bottom are mismatched? The 3 pajamas will be referred to by…

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## A prism of a bathroom sink

A trip to the ladies room of the Arclight Cinemas in the local mall revealed a somewhat unusually shaped sink. In case you’re wondering where the water drains, there’s a slit right along the back edge, shown by the blue arrow. But what happens if the drain backs up; how much water can a…

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## A Generous Uncle?

When my daughter was 6 years old, her uncle gave her this figurine, a couple of inches tall. She asked if it was made of pure gold. Well, let’s see how much it would cost if it were. At the time of this writing, gold costs about $37.88 per gram. The density of gold is…

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