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➡ Can You Solve the Burning Rope Riddle?
Popular Mechanics ^ | May 15, 2025 | Staff

Posted on 05/15/2025 9:41:05 PM PDT by Red Badger

This simple puzzle recently appeared in a members-only newsletter. Think you can crack it?

You have two ropes coated in oil to help them burn. Each rope will take exactly one hour to burn all the way through. However, the ropes don’t burn at constant rates; there are spots where they burn a bit faster and spots where they burn a bit slower, but it always takes one hour to finish the job. With a lighter to ignite the ropes, how can you measure exactly 45 minutes?


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To: ifinnegan

“They will disintegrate at twice the rate if touched in two spots.”

Nope. Again, part of the rope could burn in 5 minutes, part could burn in 55 minutes.


21 posted on 05/16/2025 3:56:38 AM PDT by CodeToad
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To: Red Badger

One of my dad’s questions when growing up...”an electric train is going north at 30 mph while the wind is blowing south at 30 mph. Which way will you the smoke go?”


22 posted on 05/16/2025 4:02:07 AM PDT by Qwapisking ("The left will rue the day they cheated Trump out of the 2020 election forever" L.Star )
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To: Red Badger

23 posted on 05/16/2025 4:28:55 AM PDT by Magnum44 (...against all enemies, foreign and domestic... )
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To: CodeToad

Total burn time is constrained to one hour. Length burned in a given time is a distraction to the problem, not disproof.


24 posted on 05/16/2025 4:34:24 AM PDT by Magnum44 (...against all enemies, foreign and domestic... )
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To: Red Badger

They make it sound like you are burning through the rope like in the image, not longways like a fuse. It’s early and I’m just getting my coffee.


25 posted on 05/16/2025 4:50:27 AM PDT by bk1000 (Banned from Breitbart)
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To: Harmless Teddy Bear

Sundial or
one Mississippi, two Mississippi,


26 posted on 05/16/2025 5:06:33 AM PDT by sasquatch (Do NOT forget Ashli Babbit! c/o piytar)
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To: Red Badger
Mark each rope into four sections.

Light both ropes.

When one rope reaches the beginning of the fourth segment and then the second rope reaches the beginning of the fourth segment, it has been 45 mins.

27 posted on 05/16/2025 5:29:38 AM PDT by yesthatjallen
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To: yesthatjallen

The ropes do not burn linearly.................


28 posted on 05/16/2025 5:30:13 AM PDT by Red Badger (Homeless veterans camp in the streets while illegals are put up in 5 Star hotels....................)
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To: CodeToad

The variable burn rate criteria stumped me. Given that, is there a solution?


29 posted on 05/16/2025 5:31:21 AM PDT by ProtectOurFreedom (“Diversity is our Strength” just doesn’t carry the same message as “Death from Above”)
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To: Red Badger

I have a watch.


30 posted on 05/16/2025 6:23:51 AM PDT by SkyDancer ( ~ Am Yisrael Chai ~)
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To: Red Badger

We had a hunting cabin, that had been an old pioneer cabin, which we leased out with hunting leases. It had a handmade stone fireplace. Some city boys took the lease for the area with it and decided to make a fire in the fireplace.

They foraged and found a long cedar post, which they brought back. They put one end in the fireplace and lit it and went about their business, assuming the part of the post in the fireplace would burn in the fireplace would burn off and they could shove it in as it burned off. Soon the whole log was on fire and setting the floor on fire. They did get it out but a long track was burned into the floor. Didn’t have much water and couldn’t carry it out because it was all on fire.

Yes, there are morons that stupid among us. Maybe their mental model of burning cylindrical objects was based on cigarettes. Or “Popular Mechanics”.

The same kind of impractical morons came up with this “puzzle”, or read it and take it as useful, or think it was worth distributing. I think articles like this make stupid people stupider.

Oh and AI is that stupid. ( Thanks/HT to freeper who tried it.)


31 posted on 05/16/2025 12:29:45 PM PDT by takebackaustin
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To: ProtectOurFreedom

Nope. Burn rates are undeterministic other than burning an entire length of rope.


32 posted on 05/16/2025 1:08:29 PM PDT by CodeToad
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To: ifinnegan

They do not burn evenly. One touched spot might burn to an end in 5 minutes and the other might take 55 minutes. Only one hour in total is guaranteed.


33 posted on 05/16/2025 1:13:43 PM PDT by CodeToad
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To: Responsibility2nd

Problem says burn rate is not constant, so you cannot time 45 minutes by any ratio.


34 posted on 05/16/2025 1:14:58 PM PDT by CodeToad
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To: yesthatjallen

Nope. No length burns linearly. Only the whole rope burns in one hour. Half a rope might burn in five minutes.


35 posted on 05/16/2025 1:17:31 PM PDT by CodeToad
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To: Magnum44

That’s correct.


36 posted on 05/16/2025 1:18:22 PM PDT by CodeToad
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To: Red Badger

What if the ropes identify as a steel cable ?


37 posted on 05/16/2025 1:21:56 PM PDT by HereInTheHeartland (“I don’t really care, Margaret.”)
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To: ProtectOurFreedom

Answer was in post 7 and the AI post but toad still hasn’t quite grasped it.


38 posted on 05/16/2025 1:23:18 PM PDT by Magnum44 (...against all enemies, foreign and domestic... )
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To: HereInTheHeartland

“What if the ropes identify as a steel cable ?”

Now that’s a conundrum! Can the ropes transition to steel cable? How long does that take? Is surgery required? Are lifetime hormone injections required? What if the steel cable wanted to de-transition?


39 posted on 05/16/2025 1:24:16 PM PDT by ProtectOurFreedom (“Diversity is our Strength” just doesn’t carry the same message as “Death from Above”)
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To: CodeToad

You are saying correct but still saying there is no answer. There is and it’s explained in 7


40 posted on 05/16/2025 1:26:36 PM PDT by Magnum44 (...against all enemies, foreign and domestic... )
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