#math puzzle

[leibnizstan]

fruit posting

[ageblue-aka-varnah-g]

Irojirai difficulty test,

Bit more advanced. Permission for y'all to maul me if I fucked this one up,

Naming this puzzle "irojirai", from Japanese "iro" and "jirai".

Tagging some folks that were active on the previous post, and inviting y'all to follow the tag #irojirai in the future, as I will be making a blog of the same name soon enough (looking for co-runners!).

@sqrt-73 @vacuously-true @dorothytheexplorothy @esoteric-merit @tousey-mousey @etoastie @andromeda-absurdity @clockw0rkvaudeville

For those unfamiliar: To solve the puzzle, you must use four colors to paint all the squares on the grid. Each square has a number written in it that lists the amount of same-colored squares around it + itself, in a 3x3 centered square mini-grid.

[facetedconfusion]

Question: people say that manhole covers are circular because they're the only shape that can't be turned to fall through itself. Am I right that this is also true of equalateral triangles?

Actually, is it true of all the regular polygons with an odd number of sides, since they don't have a "hypotenuse" (meaning here that there is no internal line that can be drawn from one vertex to another that is longer than any other internal dimension. I'm explaining this badly. But a counter example would be the diagonal on a square being linger than its width. That is not what a hypotenuse is, please tell me if there is a word.)

Of course you aren't going to make a pentagonal manhole cover, but is this saying just a misconstrued version of something like "why are manhole covers circles and not squares"?

Despite having taught high school geometry, I never TOOK high school geometry. Maybe I will try a proof.... I remember proofs, right?

[autisticaroace]

Here's a verbal arithmetic puzzle I made dedicated to Johann Carl Friedrich Gauss for his birthday on 30th of April. Enjoy; and good luck to anyone who dares take on the challenge to crack it! 😉

[395nm]

Math puzzle?

you are driving a car or riding a bicycle. you are cruising at velocity.

some distance ahead of you, a stoplight turns red. The stoplight will turn green in T seconds. You do not know the value of T.

If the stoplight is red when you reach it, you want to (be able to) stop.

you want to preserve as much of your momentum as possible, in case the stoplight turns green before you reach it

you will decelerate according to a function a(t) where a is acceleration and t is time

should a(t) be a constant function, and exponential function, or some other shape?

[danskjavlarna]

Source details and larger version.

[eri-pl]

12-ish Days of (Silm) Christmas: 8

This is a irojirai, a puzzle invented by @ageblue-aka-varnah-g

The rule is: the number is a square is the number of the squares in its 3x3 neighborhood (including itself) that are the same color as this square. The goal is to color all squares in a way that works, using the 4 colors provided. For an example, see this post.

As a bonus activity, you can explain why the resulting picture (or isn't) an appropriate house decoration.

[brightgreendandelions]

Math puzzle

what is the largest cube net that can fit on an A4 sheet of paper