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Geographical Conundrums 55!
We recently talked about which state borders we'd been across, followed by a GC! about maritime state bordersToday, let's talk about the river borders of states! There are about 60 rivers that form all or part of a state border. Let's focus on those that are part of at least three state borders (or two state borders and an international border ( Read more... ) -
Puzzle o' the Day 412!
Here's a fun one about triangles, wherein you'll derive a cool but little-known formula ( Read more... ) -
Geographical Conundrums 54!
1. (The question). Sixteen islands have populations of 10,000,000 or more. How many can you name?
2. (Follow-up). Number thirteen on the list is Salsette Island (in white, obviously, so as not to ruin question 1.). Where is that island? I didn't know before looking it up. -
Puzzle o' the Day 411!
Here's a cute one I got from one of my sources. Yes, I have sources ( Read more... ) -
Geographical Conundrums 53!
Let's reintroduce a classic GC!, then add some new twists to it ( Read more... ) -
Puzzle o' the Day 410!
In grad school, I once entered a classroom to find this puzzle; Professor Dantzig (who was just leaving) had left it on the blackboard. Can you solve it? I bet Dantzig would still give you extra credit ( Read more... ) -
Puzzle o' the Day 409!
I've been obsessed lately with Euclidea, an app that turns compass-and-straightedge constructions into puzzles. Here's a puzzle inspired by Euclidea ( Read more... ) -
Puzzle o' the Day 408!
We've had a bunch of ladder-like problems lately. So here's another one ( Read more... ) -
Puzzle o' the Day 407!
Hmmm, not much love for the last two PotD's. Maybe you want something harder? Okay!
Here's an even more challenging variant to the Crossed Ladders Problem of PotD 404! (thanks to chaithedog for reminding me of its existence ( Read more... ) -
Puzzle o' the Day 406!
Sometimes I present a puzzle because I want someone to come up with a more elegant answer than mine. So it is with this puzzle, where my solution is a tangle of algebra that mysteriously resolves into a simple expression. I hope you can do better ( Read more... )