Thursday, October 23, 2014

Did I Get This Right?

Here's this week's NPR Sunday Puzzle:
Out of a regular grade school classroom, two students are chosen at random. Both happen to have blue eyes. If the odds are exactly 50-50 that two randomly chosen students in the class will have blue eyes: How many students are in the class?
I will show you how I arrive at FOUR as my answer:

Our class has Archie, Betty, Charlie and Davy in it. Archie has BROWN eyes, the rest have BLUE eyes. Any pair with Archie in it goes in one group, all Archie-less pairs in the other group. As long as the two groups are precisely the same size, we're good to go.

A-B, A-C, A-D vs. B-C, B-D, C-D

Does it work for other numbers? I have no idea. Here's where someone else can send me the proof and I'll insert it for everyone's edification.

Here are our classmates (plus two more photos, just because they came up when I searched for "brown eye boy"):














Time for



Here are this week's picks:
Fewer than 50
 51 - 100 -- Paul
101 - 150 -- Word Woman
151 - 200 -- Joe Kupe
201 - 250 -- Ross
251 - 300 -- Magdalen
301 - 350 -- B.Haven
351 - 400 -- Curtis
401 - 450 -- Phil
451 - 500
 
501 - 550 -- legolambda
551 - 600
601 - 650
651 - 700
701 - 750 -- zeke creek
751 - 800
801 - 850
851 - 900
901 - 950
951 - 1,000
1,001 - 1,050 -- David
1,051 - 1,100 -- Henry B.W.
1,101 - 1,150
1,151 - 1,200
1,201 - 1,250
1,251 - 1,300
1,301 - 1,350 -- Mendo Jim
1,351 - 1,400
1,401 - 1,450
1,451 - 1,500

1,501 - 1,550
1,551 - 1,600
1,601 - 1,650
1,651 - 1,700
1,701 - 1,750
1,751 - 1,800
1,801 - 1,850
1,851 - 1,900
1,901 - 1,950
1,951 - 2,000
2,001 - 2,050
2,051 - 2,100
2,101 - 2,150
2,151 - 2,200
2,201 - 2,250
2,251 - 2,300
2,301 - 2,350
2,351 - 2,400
2,401 - 2,450
2,451 - 2,500

2,501 - 2,750
2,751 - 3,000
3,001 - 3,250
3,251 - 3,500
3,501 - 4,000
4,001 - 4,500
4,501 - 5,000

 > 5,000
 > 5,000 + new record
Our tie-break rule:   In the event that a single round number is announced with a qualifier such as "about" or "around" (e.g., "We received around 1,200 entries."), AND two separate people picked the ranges of numbers just before and just after that round number, the prize will be awarded to whichever entrant had not already won a prize, or in the event that both entrants had won a prize already or neither had, then to the earlier of the two entries on the famous judicial principle of "First Come First Serve," (or in technical legal jargon, "You Snooze, You Lose").  As of July 2012, this rule is officially no longer obsolete (and also I still just like having fine print).


Sunday, October 19, 2014

Hint: It's a REGULAR Grade School Classroom

Before I get to this week's puzzle, a word about the Country - Capital - Country puzzle from last week. Interesting that three of our four answers were allowed by the Puzzle Master. As Ross commented, Will Shortz must have disallowed Aruba, which "is a country the way Scotland is a country--it's a sovereign territory." Fair enough, Puzzle Master. I'm sure the nice peoples of the Solomon Islands cheered when they heard your shout out to their capital, Honiara!

Here's this week's NPR Sunday Puzzle:
Out of a regular grade school classroom, two students are chosen at random. Both happen to have blue eyes. If the odds are exactly 50-50 that two randomly chosen students in the class will have blue eyes: How many students are in the class?
I think this takes some paper and pencil. Oh, and this handy list of children's names in alpha order:

Abigail                               Kevin                           Uriah
Billy                                   Laura                           Vanessa
Carol                                  Maureen                      Willie
Diane                                 Nick                            Xerxes
Eddie                                 Olive                           Yancy
Fred                                   Petey                          Zenobia
Gladys                               Quincy
Hector                               Richie
Imogen                              Sally
Jane                                   Ted

We have an answer, which we haven't bothered to prove is the only answer. I trust Martin Gardner did that in the first place. Oh, and if you want a much harder puzzle, check out this blue-eyed monster over at XKCD.

Oh, and don't forget to send in your answers using the gray-eyed Contact Us form right here.

Let's see what Flickr has for HONIARA...














Time for



This is where we ask you how many entries you think NPR will get for the challenge above. If you want to win, leave a comment with your guess for the range of entries NPR will receive. First come first served, so read existing comments before you guess. Or skip the comments and send an email with your pick to Magdalen (at) Crosswordman (dot) com. Ross and I guess last, just before we publish the Thursday post. After the Thursday post is up, the entries are closed.

The winner gets a choice: they can receive a puzzle book of our choosing or they can ask that a charitable contribution is made in the winner's honor. As of this week, we are providing an alternative to the Red Cross. If the winner wishes, we will make a contribution to his/her NPR station. Send us the call letters and we'll do the rest.

I won this week, with 500. So let me ask you...how many people will want to work out the maths for the blue-eyed puzzle?

Here are the ranges:
Fewer than 50       
51 - 100
101 - 150
151 - 200
201 - 250
251 - 300
301 - 350
351 - 400
401 - 450
451 - 500

501 - 550
551 - 600
601 - 650
651 - 700
701 - 750
751 - 800
801 - 850
851 - 900
901 - 950
951 - 1,000
1,001 - 1,050         
1,051 - 1,100
1,101 - 1,150
1,151 - 1,200
1,201 - 1,250
1,251 - 1,300
1,301 - 1,350
1,351 - 1,400
1,401 - 1,450
1,451 - 1,500

1,501 - 1,550
1,551 - 1,600
1,601 - 1,650
1,651 - 1,700
1,701 - 1,750
1,751 - 1,800
1,801 - 1,850
1,851 - 1,900
1,901 - 1,950
1,951 - 2,000
2,001 - 2,050
2,051 - 2,100
2,101 - 2,150
2,151 - 2,200
2,201 - 2,250
2,251 - 2,300
2,301 - 2,350
2,351 - 2,400
2,401 - 2,450
2,451 - 2,500

2,501 - 2,750
2,751 - 3,000
3,001 - 3,250
3,251 - 3,500
3,501 - 4,000
4,001 - 4,500
4,501 - 5,000

More than 5,000
More than 5,000 and it sets a new record.
Our tie-break rule:   In the event that a single round number is announced with a qualifier such as "about" or "around" (e.g., "We received around 1,200 entries."), the prize will be awarded to the entrant who picked the range including that precise number, e.g., 551 - 600 wins if the announced range is "around 600." We retain the discretion to award the prize to an entrant who picked the adjacent range (e.g., 601-650) if that entrant had not already won a prize. In the event that both entrants had won a prize already or neither had, then to the earlier of the two entries on the famous judicial principle of "First Come First Serve," (or in technical legal jargon, "You Snooze, You Lose").  As of January, 2014, this rule is officially even more complicated than it's ever been, but at least it's consistent with what we actually do..