What do you think?

Chancie · 11-02-2010, 03:17 PM

That is very like what my kids came up with as a group.

We had already talked about something our old textbook called the guessing game algorithm, and

That algorithm is a lot like binary search.

So they hypothesized that it would be efficient to divide the coins into groups, and

They knew that it wouldn't be useful to divide the coins into two groups because

The still wouldn't know which pile contained the counterfeit and

They wanted something like a control, and

Having the control changed the way they searched after the first few iterations.

Anyway, it's worth noting that though the honors class came up with the naming system quickly and

They were able to predict some of the sticky places,

The other ninth grade class did very well at working together to solve this problem.

adorable · 11-02-2010, 05:27 PM

I was a history major......

Gráinne · 01-23-2011, 07:38 PM

My idea:

#1-Divide the 100 coins into piles of 50. The heavier pile has the counterfeit.

#2-Divide the heavier pile into piles of 25. The heavier pile has the counterfeit.

#3-Divide the heavier pile into two piles of 12 (24). You hold one coin.
IF the piles are equal, you have the counterfeit!
IF they are unequal, you have a "normal" coin, and the heavier pile
has the counterfeit.

#4-Take the heavier pile (unless you were lucky above) of 12, and divide it into 6. The heavier pile has the counterfeit.

#5-Take the heavier pile of 6 and divide into two groups of 3. The heavier pile has the counterfeit.

#6-Take the heavier pile of 3, and put one coin on each pan. You hold one coin.
IF the coins are equal-you have the counterfeit in your hand.
IF the coins are unequal-that heavy coin is the counterfeit.

pajama · 03-03-2011, 11:54 PM

Another please. Since I missed out on this one. (Not that I would have come up with the right answer.)

11-02-2010, 03:17 PM	#1
Chancie Senior Member How Do You Identify?: queer femme-inist Relationship Status: I'm lucky. Join Date: May 2010 Location: Western Mass Posts: 3,772 My Photo Gallery Thanks: 9,488 Thanked 14,535 Times in 2,741 Posts Rep Power: 21474855	That is very like what my kids came up with as a group. We had already talked about something our old textbook called the guessing game algorithm, and That algorithm is a lot like binary search. So they hypothesized that it would be efficient to divide the coins into groups, and They knew that it wouldn't be useful to divide the coins into two groups because The still wouldn't know which pile contained the counterfeit and They wanted something like a control, and Having the control changed the way they searched after the first few iterations. Anyway, it's worth noting that though the honors class came up with the naming system quickly and They were able to predict some of the sticky places, The other ninth grade class did very well at working together to solve this problem.

11-02-2010, 05:27 PM	#2
adorable Member How Do You Identify?: Sarcastically Preferred Pronoun?: She Relationship Status: Unavailable Join Date: Feb 2010 Location: Home of the Yankee's Posts: 752 My Photo Gallery Thanks: 1,708 Thanked 2,643 Times in 590 Posts Rep Power: 12725119	I was a history major......

01-23-2011, 07:38 PM	#3
Gráinne Senior Member How Do You Identify?: Neither, nada, out of the box Preferred Pronoun?: My name always works Relationship Status: Happy whatever happens Join Date: Dec 2010 Location: Little Rock Posts: 1,864 My Photo Gallery Thanks: 2,113 Thanked 7,386 Times in 1,457 Posts Rep Power: 21474852	My idea: #1-Divide the 100 coins into piles of 50. The heavier pile has the counterfeit. #2-Divide the heavier pile into piles of 25. The heavier pile has the counterfeit. #3-Divide the heavier pile into two piles of 12 (24). You hold one coin. IF the piles are equal, you have the counterfeit! IF they are unequal, you have a "normal" coin, and the heavier pile has the counterfeit. #4-Take the heavier pile (unless you were lucky above) of 12, and divide it into 6. The heavier pile has the counterfeit. #5-Take the heavier pile of 6 and divide into two groups of 3. The heavier pile has the counterfeit. #6-Take the heavier pile of 3, and put one coin on each pan. You hold one coin. IF the coins are equal-you have the counterfeit in your hand. IF the coins are unequal-that heavy coin is the counterfeit. __________________ The odds of going to the store for a loaf of bread and coming out with only a loaf of bread are three billion to one. ~Erma Bombeck

03-03-2011, 11:54 PM	#4
pajama Senior Member How Do You Identify?: Klingon Preferred Pronoun?: She Join Date: Nov 2009 Location: Just South of Nashvegas Baby Posts: 3,115 My Photo Gallery Thanks: 7,546 Thanked 7,478 Times in 1,809 Posts Rep Power: 21474855	Another please. Since I missed out on this one. (Not that I would have come up with the right answer.)