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?
“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.
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?”
Total burn time is constrained to one hour. Length burned in a given time is a distraction to the problem, not disproof.
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.
Sundial or
one Mississippi, two Mississippi,
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.
The ropes do not burn linearly.................
The variable burn rate criteria stumped me. Given that, is there a solution?
I have a watch.
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.)
Nope. Burn rates are undeterministic other than burning an entire length of rope.
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.
Problem says burn rate is not constant, so you cannot time 45 minutes by any ratio.
Nope. No length burns linearly. Only the whole rope burns in one hour. Half a rope might burn in five minutes.
That’s correct.
What if the ropes identify as a steel cable ?
Answer was in post 7 and the AI post but toad still hasn’t quite grasped it.
“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?
You are saying correct but still saying there is no answer. There is and it’s explained in 7
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