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I taught the Monty Hall problem today as a middle school math lesson

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https://lemmy.world/u/andros_rex posted on Feb 20, 2026 05:02

Really annoyed me that the kiddos voted to not switch, and they got the car. Getting children to understand that 13 is smaller than 12 is hard enough. I’m going to program my own evil version that only wins on switch the first time next time I do this.

https://lemmy.world/post/43359589
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https://lemmy.world/u/j4k3 posted on Feb 20, 2026 05:34
In reply to: https://lemmy.world/post/43359589

I don’t care to look it up, cause that ain’t the point of social media. What is the Monty Hall problem?

https://lemmy.world/comment/22243345
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https://piefed.social/u/prettybunnys posted on Feb 20, 2026 05:40
In reply to: https://lemmy.world/comment/22243345

3 doors.

1 is a car. 2 are goats.

Contestant picks a door. The host then shows one of the remaining doors containing a goat, then asks if you want to change your door.

What do you do?

https://piefed.social/comment/10213780
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https://lemmy.world/u/andros_rex posted on Feb 20, 2026 05:42
In reply to: https://lemmy.world/comment/22243345

Here’s the sim I used if you want to check it out!

https://lemmy.world/comment/22243433
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https://feddit.online/u/ignirtoq posted on Feb 20, 2026 05:45
In reply to: https://lemmy.world/post/43359589

Change the problem from 3 doors to a million. Kids pick a door, and the host opens 999,998 doors, leaving theirs and one other door closed. One of the closed doors is the winner. Do they want to switch now?

https://feddit.online/comment/7234317
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https://lemmy.world/u/andros_rex posted on Feb 20, 2026 05:50
In reply to: https://feddit.online/comment/7234317

That’s a good idea. I went with redoing the sim a few times and then also doing stuff with a plinko game, which seemed to help them get it.

The first couple plinko runs also were really annoying for bellcurve purposes too.

https://lemmy.world/comment/22243508
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https://feddit.online/u/tuckerm posted on Feb 20, 2026 05:55
In reply to: https://lemmy.world/post/43359589

Could you do it a few times, and then have them keep track of how often they win when switching vs not switching?

https://feddit.online/comment/7234391
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https://lemmy.world/u/LifeInMultipleChoice posted on Feb 20, 2026 06:16
In reply to: https://lemmy.world/comment/22243345

It was hard to picture looking at it in one direction for me as a kid, but after thinking about it for about 15 minutes I looked at it from the “opposite view” and for some reason it clicked.

They give you the chance to open a door 13. Your first thought is that, well it’s a 50-50 chance the door they point to is the prize because there are only 2 left. so what would it matter, but really it is 23. As your chances of being right were 13 originally, and he knows where the car is, and has to eliminate one of the doors you don’t have. Making it so now 23 of the options are out if you choose a new door, or it stays at 13 if you stay the same. So you say “thank you for the extra 33% chance at winning” and always change to the second door

https://lemmy.world/comment/22243800
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https://lemmy.ca/u/Archangel1313 posted on Feb 20, 2026 06:18
In reply to: https://lemmy.world/comment/22243433

Lol! I played 12 times in a row, and always stayed. I got the car 6 times (not in a row). I know that it’s supposed to be a 13 vs 23 probability, but it sure does seem like 5050 in the long run.

https://lemmy.ca/comment/21801358
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https://lemmy.nz/u/deadbeef79000 posted on Feb 20, 2026 06:24
In reply to: https://lemmy.world/comment/22243508

I explained this to my programmer colleagues. My explanation was lacking so they wrote a numerical simulation and ran it a few million times to be sure.

They were convinced.

https://lemmy.nz/comment/20268216
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https://lemmy.nz/u/deadbeef79000 posted on Feb 20, 2026 06:25
In reply to: https://lemmy.ca/comment/21801358

It’s not, it approaches 13.

12 isn’t quite enough goes to get a good approximation.

https://lemmy.nz/comment/20268231
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https://lemmy.nz/u/deadbeef79000 posted on Feb 20, 2026 06:26
In reply to: https://lemmy.world/post/43359589

My favorite trivia about the Monty Hall Problem is that Monty Hall doesn’t understand the Monty Hall Problem.

https://lemmy.nz/comment/20268244
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https://feddit.org/u/FuyuhikoDate posted on Feb 20, 2026 06:43
In reply to: https://lemmy.world/comment/22243800

Thanks I wasn’t sure if I understood it right.

I tried 25 times with staying

And 25 times with switching

Switching gave me a winning rate of 76% and was like “hmm… If I understand it the right way the chances are bigger if I switch right?”

https://feddit.org/comment/11623722
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https://lemmy.world/u/j4k3 posted on Feb 20, 2026 07:17
In reply to: https://lemmy.world/comment/22243800

When the first door is revealed, obviously the probabilities are unchanged. The almighty protagonist of human exceptionalism must choose the path to alter the winds of the fates. Pray the great Apollo smiles upon thy being. For speaking the word “same” is to alter the universe of satyr sophistry.

https://lemmy.world/comment/22244461
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https://feddit.org/u/killingspark posted on Feb 20, 2026 07:19
In reply to: https://feddit.online/comment/7234317

Oh this makes it so much more intuitive. I’m gonna use that in the future

https://feddit.org/comment/11624085
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https://lemmy.ca/u/Archangel1313 posted on Feb 20, 2026 07:41
In reply to: https://lemmy.nz/comment/20268231

Oh, I know…but I played another 5 rounds afterwards and now I’m ahead by 2 on cars. I think I should buy a lottery ticket on my way home tonight. I’m shittin’ clovers right now. Lol!

https://lemmy.ca/comment/21802180
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https://programming.dev/u/ChairmanMeow posted on Feb 20, 2026 09:10
In reply to: https://lemmy.ca/comment/21802180

I managed to get 3 wins and 17 losses by staying lol. I’ll hold off on those lottery tickets.

https://programming.dev/comment/22293076
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https://lemmy.world/u/fluxx posted on Feb 20, 2026 09:27
In reply to: https://lemmy.world/post/43359589

What helped me understand way back when I found out about it was using 3 cards, one car, two goats. Then have the student choosing not see the cards and you and the rest can see them standing on the other side. If the student never switches, he/she has 13 chance of picking a car. If the student always switches, it becomes obvious, especially if you see the cards, that to win he/she has to pick a goat, which is 23 chance. It makes it even more obvious with more goat cards. The students watching immediately see which card must be chosen for two situations - never swap or always swap.

https://lemmy.world/comment/22245915
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https://sh.itjust.works/u/rebelsimile posted on Feb 20, 2026 10:38
In reply to: https://feddit.online/comment/7234317

This is a good way to think about it, because the three door version makes it almost seem like the host is guessing. But if you pick door #8 and the host eliminates every door except #8 and, for some reason, #682,025, are you more confident in 8 or 682,025?

https://sh.itjust.works/comment/23877751
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https://lemmy.world/u/Speculater posted on Feb 20, 2026 11:22
In reply to: https://lemmy.world/comment/22243433

https://lemmy.world/pictrs/image/7cbda876-3c73-44b0-ba1a-c40e23683ead.png

That’s a fun sim!

https://lemmy.world/comment/22247069
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https://lemmy.dbzer0.com/u/MigratingApe posted on Feb 20, 2026 12:01
In reply to: https://lemmy.nz/comment/20268216

It’s called Monte Carlo method, I presume.

https://lemmy.dbzer0.com/comment/24527451
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https://lemmy.world/u/SuperEars posted on Feb 20, 2026 12:55
In reply to: https://lemmy.world/comment/22243508

Have you played the Cliff Hangers music to those children, because if so I love you.

https://youtu.be/HjT7bSHAHAU

https://lemmy.world/comment/22248209
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https://lemmy.world/u/andros_rex posted on Feb 20, 2026 14:04
In reply to: https://lemmy.dbzer0.com/comment/24527451

I talked a little about Monte Carlo methods too - told them about a FORTRAN (!) program I had to write in college. Finding pi by throwing darts at a dart board and looking at the ratio of hits to misses to determine area…

https://lemmy.world/comment/22249247
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https://lemmy.world/u/idunnololz posted on Feb 20, 2026 15:20
In reply to: https://lemmy.nz/comment/20268216

LOL I did this too when I first heard the solution.

I was like “no, that cant be right”. Then ran the test and was surprised by the result.

https://lemmy.world/comment/22250637
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https://reddthat.com/u/curiousaur posted on Feb 20, 2026 19:12
In reply to: https://lemmy.world/post/43359589

The issue is that this isn’t a fraction problem, it’s a statistics problem. You need sample size. You need to teach it with M&Ms or something small, and let the kids choose to switch or not switch and play 20 rounds each with that choice, then compare piles.

https://reddthat.com/comment/24895528
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