Since Twitter (now X) is no longer public, I was afraid I would not have access to new Catriona Agg puzzles, but she has put them up on Instagram, which is partially available to the public. I managed to find a half dozen interesting new brain ticklers.

# Tag Archives: Catriona Agg

# Curious Sunbeam Problem

This is a Catriona Agg problem presented by itself, since it turned out to be the most challenging one I ever tried. Usually I can solve her problems in a few minutes or maybe hours, or sometimes days if they are especially challenging. But this problem has taken me weeks and I had to rely on a non-geometric argument. The problem is full of fascinating and unexpected relationships, but I couldn’t find a way to use them to prove the answer.

See the Curious Sunbeam Problem

**(Update 5/5/2023) Alternative Solution** Continue reading

# Geometric Puzzle Mystifiers

Here is yet another (belated) collection of beautiful geometric problems from Catriona Agg (née Shearer).

# Geometric Puzzle Magic

Here is yet another (belated) collection of beautiful geometric problems from Catriona Agg (née Shearer).

# Two Equilateral Triangles

This is a most interesting problem proposed by Mirangu and retweeted by Catriona Agg:

“Two equilateral triangles share a vertex. What is the proportion red : green?”

See the Two Equilateral Triangles for solutions.

# Geometric Puzzle Mindbogglers

Here is yet another collection of beautiful, stimulating geometric problems from Catriona Agg (née Shearer).

# Geometric Puzzle Magnificence

Here is yet another collection of beautiful geometric problems from Catriona Agg (née Shearer). For some reason I found these a bit more challenging than the previous ones. Some of them required more time to “see” the breakthrough.

See Geometric Puzzle Magnificence (revised)

**(Update 11/13/2022)** **Problem #3 Solution Corrected** Continue reading

# Geometric Puzzle Marvels

Here is another collection of beautiful geometric problems from Catriona Agg (née Shearer). They never fail to brighten the day with their loveliness.

# Geometric Puzzle Munificence

Having fallen under the spell of Catriona Shearer’s geometric puzzles again, I thought I would present the latest group assembled by Ben Orlin, which he dubs “Felt Tip Geometry”, along with a bonus of two more recent ones that caught my fancy as being fine examples of Shearer’s laconic style. Orlin added his own names to the four he assembled and I added names to my two, again ordered from easier to harder.

See Geometric Puzzle Munificence.

**(Update 4/16/2020)** Ben Orlin has another set of Catriona Shearer puzzles 11 Geometry Puzzles That Drive Mathematicians to Madness which I will leave you to see and enjoy. But I wanted to emphasize some observations he included that I think are spot on. Continue reading

# Geometric Puzzle Madness

I have been subverted again by a recent post by Ben Orlin, “Geometry Puzzles for a Winter’s Day,” which is another collection of Catriona Shearer’s geometric puzzles, this time her favorites for the month of November 2019 (which Orlin seems to have named himself). I often visit Orlin’s blog, “Math with Bad Drawings”, so it is hard to kick my addiction to Shearer’s puzzles if he keeps presenting collections. Her production volume is amazing, especially as she is able to maintain the quality that makes her problems so special.

The Stained Glass puzzle generated some discussion about needed constraints to ensure a solution. Essentially, it was agreed to make explicit that the drawing had vertical and horizontal symmetry in the shapes, that is, flipping it horizontally or vertically kept the same shapes, though some of the colors might be swapped.