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Saturday, January 28, 2012

A REAL REAL Number Puzzle

Okay so here's a good one in order to make up for that last one.

A teacher thinks of two consecutive numbers between 1 and 10. The first student knows one number and the second student knows the second number. The following exchange takes place:
First: I do not know your number.
Second: Neither do I know your number.
First: Now I know.
What are the 4 possible solutions?

11 Comments:

Blogger Caleb said...

So, the lying first student doesn't actually know, he just knows four possibilities?

10:22 PM  
Blogger Luke Murphy said...

Neither of the students are lying. The first student knows both numbers, but WE only know that there are 4 possibilities.

12:23 PM  
Blogger Dad said...

Huh? Both numbers? Am I wrong in assuming that the solution is four pairs of numbers between 1 and 10 and each pair is consecutive?

12:39 PM  
Blogger Dad said...

Do the students know that the numbers are consecutive?

12:41 PM  
Blogger Luke Murphy said...

Yes, they know that the numbers are consecutive.

12:48 PM  
Blogger Luke Murphy said...

So if the first student's number is 5, then he knows that the second student's number is either 4 or 6.

12:48 PM  
Blogger Luke Murphy said...

The first student, at the end of the exchange, knows both numbers exactly. From this, you and I can deduce 4 different possible pairs.

12:51 PM  
Blogger Dad said...

Got it.

7:05 PM  
Blogger Luke Murphy said...

Anna wants everyone to know that she got it first, this afternoon. I couldn't post a comment then because the internet was down.

10:14 PM  
Blogger Dad said...

I had it yesterday morning but I'd just washed my hair.

9:16 AM  
Anonymous Uncle Don. said...

I think that this puzzle is FUBAR.

4:49 PM  

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