Joshua Greene
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37 followers
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math recommendations for a 3 year old
I was recently asked for suggestions by a parent of a 3 year old. There are a lot of different resources I could
suggest, but they really depend on the child and the parents. The main question
for customization is about the parents: what are their starting ...
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Math Teachers At Play Carnival #110 Summer Vacation Edition
Hello again math folks! I've been in the middle of a major transition, moving between Asia and North America, so haven't really had time to post recently. Putting together this month's carnival was a nice opportunity to see what everyone else has been writi...
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Some simple dice games
J3 and I played several simple games recently that I want to record. One of them, race to the top, is a variation of a more sophisticated game that can be used more generally. Digits three in a row Materials: a 100-board, 2d10, colored tiles Players : 2 Goa...
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Cryptarithmetic puzzles follow-up
I was asked to write a bit about strategies and answers for the puzzles we gave two weeks ago . BIG + PIG = YUM Because the digits in YUM are all distinct from BIG and PIG and there are only 7 letters in this puzzle, we should expect there to be many soluti...
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A bit of 3D(ish) geometry
Note: this post started out focused on two recent geometry projects. However, the Desmos Function Carnival, which I originally just included as a miscellaneous item, is also worth your time. Nets and solids The most ambitious project recently was led by P (...
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RSM International Math Contest
Sometime the first week of February, the RSM offers an on-line math competition. For the second year, I had J1 and J2 work through the problems at grade 3 and grade 4 level.  This post is about our thoughts on competition, but I end with a problem from the ...
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Cryptarithmetic Puzzles for Grades 1 to 4
Inspired by a series of puzzles from Manan Shah , I decided to have the kids play with cryptarithmetic puzzles today. In addition to borrowing some of Manan's puzzles, I also used some from this puzzle page: Brain Fun . I've included some more comments belo...
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Joshua Greene commented on a post on Blogger.
The diagram showing that the triangle and the trapezoid (trapezium, in the UK) don't fit together isn't correct: they do fit together since both of those sides have length 2. What doesn't work is that they don't form a straight line at that point.

A nice little follow-up for students is to figure out whether the shapes they form are convex (angles add up to less than 180 degrees) or concave (angles add up to more than 180). Does that fit the area conundrum?
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More Man Who Counted (gaps and notes)
As previously mentioned, we have been reading The Man Who Counted . While the story is good and there are nice math puzzles, we've found some of our best conversations have come from errors or weaknesses in the book. Here are three examples: How old was Dio...
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