Math Riddles

82 readers
1 users here now

Guidelines

  1. Riddles, not homework. This community is for people to share math problems that they think others would enjoy solving. It is not intended for helping students with homework problems or explaining mathematical concepts. Posting riddles which you do not know the answer to is permitted.

  2. Harder than trivial. While math riddles of any difficulty are welcomed, please avoid posing problems whose solution is formulaic and/or trivial.

  3. Spoiler your answers. The intent here is to let others engage in discussion without giving the answer away. It's fun to think about it, and choose when you need a hint!

  4. Text & image focus. The purpose of this community is for its members to try and solve it themselves. Video links are only accepted when they present the question but no solution. If they include a solution, feel free to post the riddle as text and to include a link to your source.


Code of Conduct

For now, code of conduct shall simply follow the official CoC from the Lemmy organization: Link

Some highlights:

founded 1 year ago
MODERATORS
1
 
 

Calculating 25 minutes by burning 2 inconsistently burning 1-hour ropes

You are given two ropes and are told that they burn at inconsistent rates, but will always take 1 hour to completely burn up. This means that cutting one of the ropes perfectly in half will not give you two smaller 30-minute ropes.

You are told that you need to approximately calculate 25 minutes by burning these ropes in some fashion.

How do you accomplish this?


Hint:

first ½ of hintI carefully chose approximately instead of precisely
second ½ of hintbecause to calculate it precisely would require that you ignite an infinite number of flames

2
 
 

Hey everyone. I’m coming from Reddit and I’m new to Lemmy, and wanted to join all of the communities that I was subscribed to on Reddit. I’m noticing that, to my knowledge, there isn’t a Math Riddles community yet on any instance. So I’ve created one.

I have some minor mod experience on Reddit, but this is definitely not something that I expect to be hardcore monitoring. I mainly just wanted to open the community to give us a space to post interesting riddles!

If there’s any Lemmy specific best-practices you’d like to see here, please let me know!