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        riddles >> medium >> checkerboard
        
(Message started by: videogamer1805 on Dec 22^nd, 2007, 1:14pm)

Title: checkerboard
Post by videogamer1805 on Dec 22^nd, 2007, 1:14pm

yeah, everyone's seen those problems where you see a checkerboard and it asks how many squares there are. you count the 1x1s, 2x2s, etc. but now, a person comes up to you and asks if you want to solve one. you think it will be so easy, so you agree. the person tells you, "there's one condition, I get to choose how long you look at it...five seconds should be fine."

you don't know how many squares there are, and you can only look at it for five seconds. assuming you're not a supercomputer android guy, and cannot count 1,523,824,603 squares per second, CAN YOU FIND OUT HOW MANY SQUARES THERE ARE? ???

hint->[hide]YOU CAN![/hide]

Title: Re: checkerboard
Post by Grimbal on Dec 22^nd, 2007, 3:11pm

It would depend on the size of the board, I guess. If you can't count how large it is in 5s, you are sure to loose.

If it is a standard checkerboard, you don't need to look at it. Maybe just to check whether it is a 10x10 or 8x8 type.

Title: Re: checkerboard
Post by FiBsTeR on Dec 22^nd, 2007, 5:17pm

on 12/22/07 at 13:14:59, videogamer1805 wrote:

[...] and you can only look at it for five seconds. [...]

[hide]Pull out your camera and take a picture. Count the number of unit squares on a side n, then tell your friend the total number of squares is n*(n+1)*(2n+1)/6.[/hide]