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Korean Job Discussion Forums "The Internet's Meeting Place for ESL/EFL Teachers from Around the World!"
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midgic
Joined: 14 Feb 2004
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Posted: Sun Apr 02, 2006 7:01 am Post subject: |
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My answer to Huck's puzzle:
1. D
2. B
3. A
4. C
5. D |
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midgic
Joined: 14 Feb 2004
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Posted: Sun Apr 02, 2006 7:09 am Post subject: |
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My answer to Tomato's puzzle:
Judy, who doesn't like songs, wore blue.
Kathy, who doesn't like books, wore red.
Laura, who doesn't like games, wore yellow. |
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midgic
Joined: 14 Feb 2004
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Posted: Sun Apr 02, 2006 7:18 am Post subject: |
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| A school hallway has 1000 lockers. The first student comes in and opens every locker door. The second student comes in and closes every second door (starting from the second one). The third student comes in and at every third locker (starting from the third one) opens the door if it's closed or closes it if it's open....the pattern continues until the 1000th student has passed down the hallway. After the 1000th student has finished, which doors are open and which ones are closed? |
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Corporal

Joined: 25 Jan 2003
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Posted: Sun Apr 02, 2006 7:19 am Post subject: |
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My answer to the hagwon puzzle:
Min Su, who picks his nose, is a retard.
Hyun Ji, whose mommy has lots of money, is narcoleptic.
Chang Hoon, who never does his homework, is gonna grow up to be a taxi driver. |
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tomato

Joined: 31 Jan 2003 Location: I get so little foreign language experience, I must be in Koreatown, Los Angeles.
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Posted: Sun Apr 02, 2006 9:04 am Post subject: |
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Midgic, I think I got yours:
the squares (first, fourth, ninth, sixteenth) will be open, and all the others will be closed.
31 lockers would be open, ending with number 961.
Here's another one:
I used to work in a pizza store where there were 10 possible toppings.
One time, I sat down and figured out how many possible ways a customer could order a pizza.
Then, once I got all the possible combinations tallied up, I realized that there was a simple mathematical formula which I could have used.
You can do it the long way or figure out the short way.
Either way is fine with me. |
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huck
Joined: 19 Jan 2003
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Posted: Sun Apr 02, 2006 4:40 pm Post subject: |
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for the pizza toppings...
10! ?
10 X 9 X 8 X 7 X 6 X 5 X 4 X 3 X 2 X 1 ?
this is just a guess.
also, for the lockers, i would assume that all of the prime numbers would be closed.....and any number that has an odd number of factors....but i'm too lazy to search for all of those numbers right now. |
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tomato

Joined: 31 Jan 2003 Location: I get so little foreign language experience, I must be in Koreatown, Los Angeles.
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Posted: Sun Apr 02, 2006 6:09 pm Post subject: |
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Hello, Huck!
on the pizza puzzle
Sorry, the answer is not 10 factorial.
Hold the idea, though. You might want to ask how many ways you can arrange 10 Easter eggs in a Korean egg carton. For that problem, you have the right answer.
Ever heard of the 20th Century German composer Arnold Schoenberg?
He devised a system whereby the composer takes the 12 tones of the octave (C, C#, D, Eb, E, F, F#, G, Ab, A, Bb, B) and arranges them in the order which he or she wishes. This arrangement is known as a tone row. The composer then bases the new composition on that tone row.
How many possible tone rows are there?
12 times 11 times 10 times . . . well, I think you get the idea.
(That's also how many ways you can arrange 12 Easter eggs in an American egg carton.)
Now I'll give you a hint on the pizza puzzle:
There are 3 valves on a trumpet, so there are 8 possible fingerings on the trumpet:
�ۡۡ�
�ۡۡ�
�ۡܡ�
�ۡܡ�
�ܡۡ�
�ܡۡ�
�ܡܡ�
�ܡܡ�
(All 8 fingerings are not used, because some of them are out of tune.
It's still a good math puzzle, though.)
There are 9 holes on a recorder, so there are 512 possible fingerings on the recorder.
For counting possible pizza orders, the principle is the same.
on the locker puzzle
I think it's squares and not prime numbers.
I opened the Excel program and made 20 rows and 20 columns.
I found that 1, 4, 9, and 16 were open after the 20th student passed by and all the others were closed.
We haven't heard from Midgic yet, though.
Midgic, what is your verdict?
Last edited by tomato on Wed Apr 05, 2006 3:53 am; edited 1 time in total |
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midgic
Joined: 14 Feb 2004
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Posted: Sun Apr 02, 2006 8:20 pm Post subject: |
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We haven't heard from Midgic yet, though.
Midgic, what is your verdict? |
Ok, the verdict is that Tomato is exactly right, and Huck is partially right.
The numbers with an odd number of factors will be open. Those numbers are the perfect squares since all other numbers have factors which match up with other factors. That is, factors always come in pairs.
The pizza problem answer is 2 raised to the power of ten, so 1024 different combinations of toppings, the most plain one being the pizza without any toppings at all. |
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huck
Joined: 19 Jan 2003
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Posted: Sun Apr 02, 2006 10:37 pm Post subject: |
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Hmm...I think it's time I stopped trying to do these off the top of my head...
I figured out the answer to the pizza question when I was lying in bed this morning using this idea....
I have 3 colors, red, blue, and yellow....how many different combinations are there? If my pizza answer was right, then it should've been 3 X 2 X 1 = 6, but there's actually 8 combinations...
so I realized that I was mixing up equations learned from statisitcs class.....so, like midgic said...2 to the 10th power... |
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midgic
Joined: 14 Feb 2004
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Posted: Sun Apr 02, 2006 11:45 pm Post subject: |
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| You work in a shop that sells 1-gram weights. People come in to the store, put a number of 1-gram weights (possibly as many as 1400) in a weightless bag, and come to your counter to pay for them. You have a balance scale and a set of weights to check how many 1-gram weights are in the bag. You need to be able to check up to 1400 1-gram weights. What's the minimum number of weights you need in your set? What are the different weights you need in your set? |
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tomato

Joined: 31 Jan 2003 Location: I get so little foreign language experience, I must be in Koreatown, Los Angeles.
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Posted: Mon Apr 03, 2006 7:26 am Post subject: |
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You got a killer there, Midgic.
Here is what I came up with:
According to my projections, 1023, which is 2 to the 9th power minus 1, will be:
1 2 4 8 16 32 64 128 256 512
But from that information, I cannot figure out what 1400 would be.
Not unless we just add on a 1024.
Was I on the right track? |
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midgic
Joined: 14 Feb 2004
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Posted: Mon Apr 03, 2006 8:33 pm Post subject: |
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According to my projections, 1023, which is 2 to the 9th power minus 1, will be:
1 2 4 8 16 32 64 128 256 512
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Hi, Tomato.
That's a pretty good answer, but I think it's possible to do it with fewer weights. Hint available upon request.... |
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robot

Joined: 07 Mar 2006
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Posted: Mon Apr 03, 2006 11:06 pm Post subject: |
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roman numerals might be a good direction
6 weight measurements needed: I, V, X, L, C, D, = 1, 5, 10, 50, 100, 500
1 = 4 needed
5 = 1 needed
10 = 4 needed
50 = 1 needed
100 = 4 needed
500 = 2 needed
16 weights needed in total. i guess you can also use an M (1000) and have the same number.
500 = 1 needed
1000 = 1 needed
- - - - - - -
9 = 5 + 1 + 1 + 1
99 = 50 + 10 + 10 + 10 + 10 + 5 + 1 + 1 + 1 + 1
999 = 500 + 100 + 100 + 100 + 100 + 50 + 10 + 10 + 10 + 10 + 5 + 1 + 1 + 1 + 1
1400 = 500 + 500 + 100+ 100 + 100 + 100 + 50 + 10 + 10 + 10 + 10 + 5 + 1 + 1 + 1 + 1
- - - - - - -
ROBT. |
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tomato

Joined: 31 Jan 2003 Location: I get so little foreign language experience, I must be in Koreatown, Los Angeles.
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Posted: Tue Apr 04, 2006 4:57 am Post subject: |
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Migdic, just answer a few questions:
--Does it have to do with prime numbers?
--Does it have to do with base 2?
--If not, does it have to do with base 10?
--If not, does it have to do with any other base system?
--Does it have to do with squares?
--Is there anything special about the number 1400, or was it chosen at random? |
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midgic
Joined: 14 Feb 2004
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Posted: Tue Apr 04, 2006 6:05 am Post subject: |
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| Quote: |
1--Does it have to do with prime numbers?
2--Does it have to do with base 2?
3--If not, does it have to do with base 10?
4--If not, does it have to do with any other base system?
5--Does it have to do with squares?
6--Is there anything special about the number 1400, or was it chosen at random?
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1 no
2 no
3 no
4 sort of...
5 no
6 nothing particularly meaningful about 1400
Tomato, your answer using powers of two is very much on the right track. That would require 11 weights. There are two solutions (at least) that use fewer than 11 weights. Hint: The scale is a balance scale, so it has a left part and a right part. The weights can be placed on either side. |
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