Level Up Just By Eating: Chapter 106 – First half of the 1 in 5 room

Published by Shiro on

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 ――On the last chapter――

 We have to go through 5 rooms.

 However, one of the rooms has deadly poison.

 There’s a detoxification scroll, but you can only use it in four rooms.

 Which room would you use?

 ――And now, back to our usual schedule――


 We went inside the first room.

 The height is 2 meters, and there stands a shallow rectangular stone door with a width of just over two meters inside.

 Seems like you have to open from the middle, and you can see a thin line in the center of the door.


「How do we……open this door?」


 Muttering so, the door shone white.

 A handprint appeared.

 And we heard a voice.


〈The door here opens when everyone places their right hands here together!

 So if you lose the game, everyone gets to die together!

 Fortuna-sama doesn’t want to see any cruel development of breaking your friendship, Fortuna-sama is so gracious!〉


 What an evil idea.

 Laura murmured.


「Based on the probability……。

 We should pass the last room without using the scroll.」

「That’s no good.」

「Why not?! Based on probability, isn’t that the best option?

 If there’s poison gas in one of the four rooms, then we can just break through with zero risk?!!」



 Not wanting to retort her at all, I stared at her like staring at a dumb child.


「What’s with that look?!

 Am I not right?!

 Isn’t my calculation perfect?!」


「If this is the only time we’re going to pinpoint this, then Laura-san would be correct……?

 That’s if….we’re speaking in terms of probability.」

「I think Laura-san is right as well, probability wise.」


(Blink blink.)


 Marine’s the only one not understanding what we’re talking about, but everyone else agreed with Laura.

 Apart from Laura and Lindis, but even Lolona and Femille who I have high hopes agreed as well…?

 I was slightly confused, but I regained my calmness.


(Even on earth, it was around the 1600’s that the theory of probability was debated.)


 Only during the 1900s that people started researching and understanding more.

 I explained briefly.


「Let’s use a lottery to simplify this――。

 Let’s say you have 5 lottery, and one is a  hit. So the probability is one in five right?」



「That’s right.」



「Then let’s say one of them is a miss, so now we have 4 left.

 So now the probability of winning is a quarter right?」



「However, in order to reach this 1 in 4 chance, you have to miss one lottery first to get it right?」

「Then if you just win from the first try, the rest is a miss!」


「Basically, the probability of winning the 2nd time is calculated by multiplying ⅕ with ¼.」


「I see now……!」

「I’m impressed with Keima-san’s insight every time……!」


「Wait a minute! How does Lolona-chan and Femille-chan understand that?!

 I don’t understand anything though?! The story felt like listening to a fallen angel!

 Even Lindis-chan doesn’t understand right?!」


「That’s right!

 There’s too much terminology like ¼ or ⅕!」



 Marine went behind the two by skipping.


「So it’s 3 to 3! We shall follow based on the majority vote!」

「How are we going to teach Marine when she’s still so young to understand.……」

「Even if it’s a child or an adult, a vote is a vote! There’s no difference in value!」


 Laura suddenly turned into an actual Goddess by saying such a thing.

 It kinda pisses me off when she’s suddenly acting like an actual Goddess.

I pinched her cheek.




「Anyway, this is the same with the lottery I just described.

 The probability of hitting a poisoned room remains the same no matter which room you choose.

 However, if you think of it normally, the room with the poison is――――」


「It’s probably the last room.」

「Logically speaking, breaking through without any risk is impossible……」


Lolona and Femille nodded based on my opinion.


「In the end, which room should we psas without using the scroll?

 As far as I can tell, I don’t care if we don’t use it in the last room.」


「……Let’s not use on the fourth room.」

「The fourth?」



 I used a scroll.

 It envelops myself with a detoxification spell, then I adjusted my hand on the imprint. 

 Everyone did the same.

 The announcement voice was heard.


〈So you decided to use the scroll?!

 So, this room――!〉


The door opened.


〈has no poison! Too bad!

 You have wasted your scroll!〉


 We went straight ahead.


(Tap tap.)


 Laura whispered.


「Hey Keima, why would you choose the fourth one?」

「If you think about it logically, the fourth door has the lowest chance.」


「This game—–I’m sure most people would either choose the ‘first’ or the ‘last’ room.」



「People who choose the ‘last’ room thinks that it’s a risk-free route.」


 I’m sure most if not all would choose that!」


「On the other hand, the ‘first’ route is 80% safe.

 I’m sure this is the only one that people would decide.」


「You’re right.

 It’s difficult for someone who can’t decide to make a decision, so they might as well just bet on the first room.」


「Someone who’s leaving it to luck would use a scroll on the second door.

 The 3rd as well.

 The 4th.

 However, after the 3rd room, one of the friend might propose “Let’s just make a decision right now”」


「I understand that the first and last are dangerous….but why is the fourth the safest?」

「Remember what the Goddess Fortuna said? “It’s important to secure human resources in these trials”.」



「As I said from the beginning, if you play this game based on luck, the ‘first’ and ‘last’ rooms are the only rooms that you won’t use the scroll.

 If you get to open the 3rd or 4th room, there’s a high chance that you can’t due to “broken friendship”.

 Which means――」


 Lolona interrupted me.


「The ability to open the 4th room without using the scroll is based on whether you can calmly judge when facing this abnormal trial.

 Only a charismatic member would be able to persuade their friends.

 Thus, you need someone like that to be able to pass these trials――。

 is that what you’re trying to say, Keima-dono!」


 Lolona’s eyes were shining brightly.

 She completely respects me.


「To be able to think that far.…………As expected」


Even Femille looks at me with respect.

Laura then said.


「Meaning we can overcome this trial――――is thanks to me?」




「But isn’t that the case?!

 Charisma = me!

 Keima is the one thinking about everything, but it’s up to me to bring everybody together!

 Wasn’t I the one who calmly thought of things and suggested the idea first?!」


「My ass.」



 I jabbed lightly on Laura’s jaw.

 A light Knock! Sound was heard.


 ――We have perfectly read the situation.

 And the poison is in the last room.

 So, if we passed through the fourth room without using the scroll, the story would’ve ended.

 Nevertheless, we will end up using the scroll in the fourth room.

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Thank you so much to all my patron supporters who have been helping me since the beginning, and to those who are helping me right now as well.


Wave your arms around like a kawai twat


Mio · 28th July 2020 at 3:31 AM

Thanks for the chapter desu~

    Mio · 28th July 2020 at 5:50 AM

    Math is hard…it makes my head hurt.

    Sucking in the poison from the rooms seems much easier.

      Xias · 28th July 2020 at 6:58 AM

      Well, the math is wrong there anyway.
      5 tickets = 4 fails, 1 win

      To win in the 2nd round you need to fail the 1st round.
      That is correct.
      But 1/5 * 1/4 is incorrect.

      There are FOUR = 4 tickets that will fail, not 1.
      So you will fail 4/5 times and only win 1/5 times in the 1st round.

      Hence to win in the 2nd round you must fail the 1st round (chance: 4/5) and then win in the 2nd round with the 1 winning ticket out of the 4 remaining tickets (1/4 chance).
      So the chance to win in the 2nd round is:
      4/5 * 1/4 = 1/5

      So basically the chances for any ticket to be the winning ticket is the same.
      But that is only the case if there is no manipulation by whom hands out the tickets.

      Same is with the poison filled room.
      Any of the 4 rooms has a chance of 1/5 to be the poison room – except if the “overseer” can manipulate the results – which is most likely the case seeing that cheating “magician” with his cards before.

Xias · 28th July 2020 at 6:39 AM

Thanks for the chapter.

I bet the whole thing is rigged.
The “overseer” of this trial can either adjust which room the doors will connect to or they can release the poison during the short period they respond to the participants about their choice to use a scroll or not.

In other words you cannot pass the trial to begin with unless the “overseer” decides or is ordered to let you pass.

Now my guess is that the MC has “revealed” their decision when to use the scrolls on purpose and actually has prepared fake scrolls for room 2, 3 or 4 for everyone.

The “overseer” will think they used their 4 scrolls and have the “last” room filled with the poison.
Then they suddenly pull out a “fifth” scroll of anti-poison which will shock the “overseer”.

Finally the MC will reveal that they used a fake scroll in one of the other rooms because he had already expected for the “overseer” to cheat.
With that they would then safely pass the poison filled 5th room and pass the trial.

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