Mad old lady riddle

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Grammar Geek

#545081 Tue, 22 Jul 08 07:29 PM

Sorry, I misread. I though you wrote "1/2" not "1/20" and that you had misread what I had written thinking I mean it would resolve itself as 1/2.

Grammar Geek

Joined on Tue, Jan 10 2006

Pennsylvania, USA

Veteran Member (15,583)

Barbara, who answers in American English.

Ant_222

#545088 Tue, 22 Jul 08 07:39 PM

GG: You were right. First I indeed thought you meant that thing equaled 1/2, which is reflected in the first sentence of that post of mine. A second later, however, I understood you had written a multiplicative series, so in the second sentence I wrote what it equals to. That post is simply self-contradicting ;)

Anyway, 1/20 is not the right answer.

Ant_222

Joined on Sun, May 21 2006

Podolsk, Russia

Contributing Member (1,547)

Grammar Geek

#545109 Tue, 22 Jul 08 09:10 PM

Ah, the old "Edit your post after I had already read it and responded trick"! Now at least I know I'm not going buggy.

Grammar Geek

Tanit

#545116 Tue, 22 Jul 08 10:04 PM

1/19?

Tanit

Joined on Mon, Jul 31 2006

In the middle of the Mediterranean Sea

Senior Member (2,142)

A man can do only what he can do. But if he does that each day he can sleep at night and do it again the next day. (A. Schweitzer)

Ant_222

#545329 Wed, 23 Jul 08 07:37 AM

GG: "Now at least I know I'm not going buggy."

Yeah, but it looks like that I am! I don't remember editing that post :)

Tanit: "1/19?"

Nope :))

Ant_222

Insider

#545838 Thu, 24 Jul 08 12:12 PM

Ha ha ha. Ant, you are wit! :) But there is no dinosaur in the world, if there were one your chance of meeting it would be either yes or not.:p
I confess that im next to zero in probability theory, just trying to use kind of common logic. So I am to understand from your messaging with GG that the answer is not 1 to 2?
To think logicly, there is always only two options for passengers: either the old lady's sit or their own sit. As far as their ticket shows their exact place i dont think number of sits in the bus plays a role in the chances of early siters or the last siter. Accordingly the last place is either the last person's or the mad lady's, there is no other option. So why 1 out of 2 is not right? I can't see what I am missing.:(

Insider

Joined on Mon, Jul 18 2005

Auckland, NZ

Junior Member (87)

M.A.Q.

Numbers

Ant_222

#545903 Thu, 24 Jul 08 02:22 PM

Hi, Insider.

Glad to see you don't give up.

"So I am to understand from your messaging with GG that the answer is not 1 to 2?"

I didn't say that.

"To think logicly, there is always only two options for passengers: either the old lady's sit or their own sit."

No, if their own seat is occupied, they take a random vacant seat.

"As far as their ticket shows their exact place i dont think number of sits in the bus plays a role in the chances of early siters or the last siter."

Oh, it does. The more seats, the more chances for the last passenger to sit on his seat. Consider two passengers and two seats. The answer is 1/2. And if there are three seats? The answer changes to 1-1/3 = 2/3. Try to understand that.

"Accordingly the last place is either the last person's or the mad lady's, there is no other option. So why 1 out of 2 is not right?"

Well, for the same reason that you don't meet a dinosaur in 50% of times visit a bakery ;) And you're not right about the last place. Anybody can accidently take it. For example, the mad lady took the second passenger's seat. The second passenger, having found his place occupied, took the last passenger's seat.

Ant_222

Numbers

Ant_222

#546384 Fri, 25 Jul 08 08:33 PM

All right. Hereby I announce a three-day countdown period, on the expiration whereof, if no solution is provided, I shall disclose the answer and the way I came to it. For all those who are interested.

Ant_222

Grammar Geek

#546393 Fri, 25 Jul 08 09:24 PM

I would suggest that anyone who is interested has already commented. You said give it five minutes of thought, and I have done so. I'm not investing any further thought. You may as well post the answer now.

Grammar Geek

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