Rhymes With Fuchsia

Sunday, September 07, 2008

Back to School: A Contest

All day I've been thinking about today's post, and nothing's been coming to me — or rather too much has been coming to me, none of it appealing. Knitting, meh. Spinning, eh. Plastic flags, feh.

Which means it's time to fall back on plagiarism, er, I mean judicious borrowing, again. Miss B's math teacher is easing the class into the regular routine, which means over the weekend she had "fun" homework, specifically the following puzzle. Send your answer to rhymes with fuchsia [aht] cahmcahst [daht] net. There could be yarn riding on this; I'll decide what tomorrow, which will give me two posts for the price of one.

Al, Bob, Carl and Dave are all on the same side of a bridge they need to cross, but it's dark out and they have only one flashlight between them. The bridge can hold at most two people at a time, and whoever is crossing the bridge must have the flashlight with them. Each man walks at a different speed, so that each takes a different amount of time to cross the bridge:
A - 1 minute
B - 2 minutes
C - 5 minutes
D - 10 minutes
If two men cross together, they must walk at the slower man's speed.

They have 17 minutes to get all four of them across. How do they do it?

Note 1: this is a perfectly straightforward puzzle with no tricks. The flashlight can't shine a long way and can't be thrown. The men can't carry each other. The puzzle requires no math skills except logic and simple addition, which would explain why I was able to solve it.

Note 2: anyone who sends me an answer will be entered in the contest, even if their solution takes more than 17 minutes. The winner will be drawn at random. However, the first person to send me a correct answer will get a little something also.


  • Poor Al-- he gets to walk everybody over, because on the way back it'll only take him a minute each time! It'll still take 'em 19 minutes total though... I must be missing something! (a brain?)

    By Blogger Joan, at 4:27 AM  

  • I think Al should just carry everyone across it one by one, and then they'll have no time worries at all. Al may have a bad back, but he needs to be willing to make some sacrifices for math, no? ;) Lol!

    By Blogger Kris, at 2:56 PM  

  • Al and Bob cross - 2 minutes.
    Bob stays and Al returns - 1 minute.
    Carl and Dave now cross while Al stays behind - 10 minutes.
    Bob now returns to start - 2 minutes.
    Al and Bob now cross - 2 minutes.


    By Blogger Chris H, at 8:44 PM  

  • You are a torturess! We (all three of us!) couldn't get it lower than 19 minutes... but I get it, now that we read Chris H's! She is so smart... Hey, what was that plant??????

    By Blogger knitnzu, at 9:28 PM  

  • Enter me, please... even though I saw the answer! :)

    By Blogger Aine, at 10:27 AM  

  • Where were they going in the middle of the night, anyway?


    By Blogger Cookie, at 2:21 PM  

  • I feel a little less smart now... This is like the 3rd grade problems my J got last year with the animals that had x hoofs and y noses and b ears and 42 toes and how many animals were in the zoo and AHHHHHH... sorry....

    By Blogger CDG, at 5:15 PM  

  • Yep, I came up with the same answer as Chris H. I'm the dork that always loved logic and word problems!

    By Blogger Danielle, at 6:52 PM  

  • Not only was I unable to solve the problem, I had to read the solution four times to understand it. Whimper. Oh, and did I mention? -- I have a Masters degree in Statistics. Beyond embarrassing.

    The yarn looks delightful; please enter me in the contest.

    By Blogger Wool Enough, at 7:55 PM  

  • I was going to tell this one to people at work today (and I read the answer in the comments last night) but I could not for the life of me remember the answer. So I'm reading it again, and we'll see if the brain is functioning tomorrow. Maybe caffeine is in order for solving this.

    By Blogger Susan, at 8:54 PM  

  • Lol...well clearly from my answer you can tell I didn't read here first. Chris is one smart bridge crosser and now I can stop pondering on this one.

    By Blogger textilejunkie, at 11:11 AM  

  • Owww - these darn things hurt my brain! I think they should make slow poke Dave hitch a ride with the farmer who's trying to cross the river in his boat with his fox, chicken and sack of grain - solves everybody's problem crossing that darn river.

    By Anonymous Chris, at 7:11 AM  

  • I started hearing Charlie Brown's teacher talking in my head as soon as I started reading -- the reason that I don't help the kids with their math homework past, say, third grade.

    But I like yarn.

    By Blogger Ruth, at 7:19 AM  

  • Yep.. a and b go 3
    then c and D go 12
    and then B and a 2

    That makes 17!
    Gotta love these logic puzzles

    By Blogger Sorka, at 9:04 AM  

  • I thought at first it was the Bridges of Koningsburg ... phew!

    I'd love to enter the contest despite my mathlessness.

    ~ Gwyndolyn O'Shaughnessy (no URL)

    By Anonymous Anonymous, at 5:04 PM  

  • Roxie enters at the last screaming minute. Still can't figure the sucker out but logic was never my strong point anyhow. It took fourty seconds. Bob summoned a dragon who lighted the whole area with his flaming breath and they all ran across "like goddamn bastards. Pardon my French."

    By Blogger Roxie, at 11:09 AM  

  • Oh, shoot...ya, I got the answer, but only this minute realized that I'd posted it instead of emailed it... None so smart on my part! And so sorry to all who would've preferred to work it out on their own.

    By Blogger Chris H, at 3:48 PM  

  • i always hated problems like that, more because i could never see the point in solving them. by the time the 3 guys figure out what order to go in, the alien man-eater has already caught up to them :)

    By Blogger the boogeyman's wife, at 3:50 PM  

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