So, Brian had his little brainteaser last week and we got a bunch of comments and it got me thinking.  Why don’t we give away some prizes for people who participate in the brainteasers?  Coincidentally, I happen to have a brand new CG15 ‘First Run’ wedge sitting at my desk.  The first 250 CG15s we ever made were marked with a first run logo and I have one to give away.  Here is how we are going to work the contest.  Every week, Brian is going to post a brainteaser.  Every person who posts a solution (whether right or wrong & no spam) will be entered to win the wedge.  At the end of Brian’s 5-6 blog series, we will announce the winner.  The first person to post the correct answer each week will also win a Cleveland Golf Tour Hat.  Get your comments in and hopefully, you will be our winner.  On to Brian’s blog…


Our new hire, Tom, is in the building ready to design, analyze, and test golf clubs…almost.  The first part of his training, however, is to spend a week down on our production floor in our assembly, polishing, quality control, shipping, and repair departments.  This will introduce him to the many steps it takes to create golf clubs, as well as show him all the hard work put in by his new coworkers.  Here are Tom’s thoughts after a week downstairs:

After spending a week downstairs working in the aforementioned departments, a few things really struck me.  First off, although everyone I spoke with on the manufacturing floor referred to their current workload as “light” I still felt that large quantities of equipment were passing through the departments on a daily basis.  I wonder what it looks like while “busy”.  This experience was also a good introduction into all of the terminology and lingo that is used in the golf industry and how to measure and analyze this information.  Finally, being an engineer, I realized that the work put in by my coworkers in R&D and all of the subtle changes that are made to a design drastically affect the day-to-day work of numerous individuals and countless equipment.

All told, the experience was beneficial.  I learned a lot of valuable skills and met a variety of good people.  Now off to R&D, Here’s Brian:

If you remember (or read the last blog), I left you with a logic problem I asked Tom during his interview (I will leave you with one each week).  Below is this week’s logic problem, along with the solution to the one I gave last week.

Coin Company:  You have 7 coin machines all making identical, 10 gram coins.  One day, one of them breaks and starts making 9 gram coins.  You have to figure out which one is broken by weighing some amount of coins, but you can only take one weight measurement.  What coins do you weigh and why?

Last Week’s

The Pond:  You’re in a boat in a small pond.  You drop the anchor from inside the boat to the bottom of the pond.  Does the water level in the pond rise, lower, or stay the same?

Answer:  The water level lowers.  This is because when the anchor is in the boat, the anchor is displacing (pushing up) water equal to its weight. When the anchor is sitting on the pond floor, it displaces water equal to its volume.  The anchor is denser than water, so the water displaced by the anchor’s weight is more than that displaced by its volume. Since it’s displacing less water when sitting on the pond floor, the water level will be lower. (John says: Feel free to google Archimedes principle and ‘eureka’ to read the probably false story of how Archimedes discovered this principle and more detail on how to apply it.)

Categories: R&D, THE LATEST

93 Responses so far.

  1. Glenn says:

    you should be able to feel a difference in one coin if it is lighter than the rest. Weigh the ones you suspect after feeling them.

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  2. Rich says:

    Number the machines from 1 to 7. Take 1 coin from machine 1, 2 coins from machine 2, 3 coins from machine 3, etc.

    Weigh all the coins together and subtract that from 280g. Whatever the difference is tells you which machine is making 9g coins.

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  3. Chris says:

    Weigh all the coins at once, one from each machine, and it will weigh 69 grams. Remove 1 coin, if it then shows an even number that is the lighter coin. Repeat this process until the scale shows an even number or the lighter coin is the only one left.

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  4. Frank Cordero says:

    Have Machine 1 do 1 coin, Machine 2 do 2 coins, Machine 3 do 3 coins, #4 do 4, #5 do 5, #6 do 6 and #7 do 7. Whichever one produces a product that is less than 1 gram of what it should weigh, 10, 20, 30…70 is the defective machine.

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  5. Howard says:

    Label the machines 1 though 7. Take 1 coin from #1, 2 coins from #2, 3 coins from #3, etc. You will have a total of 28 coins that should weigh 280 grams. Subtract 280 grams from the total weight. The difference will tell you which machine is broken. For example, if the total weight is 273 grams, machine #7 is broken.

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  6. Berkley says:

    I would just use my extra-sensory powers to sense which machine was defective!

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  7. MJ Martin says:

    I have no idea, but I would sure love to win the club.

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  8. connie says:

    Try to use one of each of the seven in a vending machine. The vending machine should kick out the lightweight coin… then weigh it to see if it’s 9g.

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  9. lee says:

    weigh six of the coins, if the weight comes up as 60 grams the one coin you left off is from the faulty machine however if 59 grams comes up the faulty machine coin is in your pile. Continue removing one coin at a time until the weight is an even number at which point the last coin you removed is from the faulty machine.

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  10. George Afflerbach says:

    Twenty-eight coins. One of machine 1; two of machine 2; three of machine 3 and so forth. The machine making the wrong coins will be the one equivalent to the difference from 280 grams.

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  11. DD says:

    In school I hated reading problems…can you shake it up a little? I don’t know this week ‘s answer but I would have known last weeks about the water displacement and the anchor. I would love to win the club…Cleveland is the BEST!

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  12. mark says:

    Take 1 coin from the first machine, 2 from the second, 3 from the third and so on. That will give you 28 coins that should have weighed 280g if all machines were working. Subtract the measured weight from 280 and that will correspond to the machine that is defective.

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  13. anish says:

    logic problems arent my thing, but retyping the correct answer as others have already written correctly isn’t either. but i love the cg15 wedges, so fingers crossed!

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  14. Chris says:

    I would set up my scale for 70 grams. With a little bit of a process of elimination, you will find your broken machine with this method.

    Get 10 coins each from machines 1-7. Weigh each stack of 10 coins from each machine until your weight does not equal 70 grams. This stack would belong to the broken machine.

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  15. Peter Lucier says:

    No clue but I like the clever solutions proposed so far, I really just want to win the club!

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  16. Paul Criscuolo says:

    I would take a progressive amount of coins from each machine. that is one from #1, 2 from #2… (1+2+3+4+5+6+7= 28 coins). The total weight if all the coins were correct is 280 grams. By weighing them, the difference from 280 grams , identifies the machine. An example: the weight is 275 grams or 5 less. That would mean #5 is defective,

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  17. Jordan says:

    those guys beat me too it…1 coin from machine 1, 2 from 2, 3 from 3, etc…

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  18. Michael Thomas Ellington says:

    Just saw the blog. Many have the answer — 1 coin from machine 1 and 2 for machine 2 etc is the solution

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  19. Wes says:

    Simply sample one coin from each machine individually and they weigh them. the one that is not 10 grams is the one that is off.

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  20. Brad Torres says:

    Take the corresponding number of coins to the machine number. Machine 1 do 1 coin, Machine 2 do 2 coins, Machine 3 do 3 coins, #4 do 4, #5 do 5, #6 do 6 and #7 do 7. Whichever group of coins does not have a total weight equally devisible by 10 grams will give you the defective machine.

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  21. Craig M says:

    Have every numbered machine produce that machine’s number of coins… number one produces one coin, number two produces two coins, number 3 produces 3 etc……the total weight of all these coins should be 280 grams when they are weighed all together. Whatever weight less than 280 gs the whole total is will be the answer. I.e. if it’s 6 grams less it will be number six, if it’s three grams less it will be number 3.

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  22. Dave M says:

    Seeing how I am the boss. I would hire somebody to do this for me. Problem solved.

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  23. Todd says:

    someone beat me to it…1 coin from machine 1, 2 from 2, 3 from 3, etc… That’s the approach to the answer

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  24. Rob says:

    Same as #s 20,19,17,etc…

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  25. Dylan Truax says:

    Sorry Evans i meant to say good job, I just said you were lucky because i knew the answer but I didnt get it entered until a couple minutes after you and when I was writing the answer it only showed 2 entries so I thought I had got it first. Props brother…

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  26. Evan Levy says:

    Take 1 coin from each machine and mark them 1-7 accordingly, and weigh them. If each was correct weight, it should show 70 grams (7 machines x 10 grams) opposed to 69 grams. Remove 1 coin leaving the rest on the scale and see if the weight drops to 60 grams (meaning you found the defective machine) or 59 grams (meani…ng you have an accurate machine). Repeat until you get a measurement of 60 grams.

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  27. John K says:

    In honor of the CG15 wedge I’d like to win, I agree with entry #15 above. I’m sure there’s an answer for this, and I’ll hope to figure it out accurately after I win the wedge.

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  28. Brian says:

    It never states that all the machines are running simultaneously, so I’m going to assume only two machines are running. Weigh one……. problem solved.

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  29. Rod H says:

    I posted this on FB, but maybe it should be here.
    So many are on the right track, but it can be done with only 21 coins – 1 from machine 1, 2 from machine 2, 3 from machine 3, 4, 5, 6, and you don’t need any from #7. If machines 1 through 6 are okay it will be 280g. If machine 7 is okay, then the difference in weight in grams from 210 will be the machine number.

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  30. Dave says:

    So many already got the solution. Great job.

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  31. Keith says:

    Assign one co-worker to each machine. Treat all your co-workers to a gumball machine with a coin from the machine assigned. Whichever person that doesn’t end up with a gumball at the end is the one who gets to fix that machine.

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  32. Craig says:

    With 21 coins – 1 from machine 1, 2 from machine 2, 3 from machine 3, 4 from machine 4, 5 from machine 5, and 6 from machine 6. Weigh these 21 coins, if the weight is 210g then machine 7 is the faulty machine. If the weight of these 21 coins is less than 210g, then the difference between 210g and the weight is the number of the faulty machine.

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  33. Phil Warnick says:

    Use coin stamps from machine 1×1, machine 2×2 and so on up through and including machine 6×6. This will equal 21 coins. Take ONE weight. Since each coin should weigh 10grams, the total should be 210grams. Compare your actual sum total to that of 210grams, the difference will direct you to the faulty machine. If there is no difference, machine 7 is faulty.

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  34. Mike D says:

    I came up with the same solution as several other people:

    Take 1 coin from the 1st machine, 2 from the 2nd, 3 coins from the 3rd, etc… Weigh the entire 28 coin pile at the end of collecting and how ever many grams are missing from the 280 gram total, that number machine is malfunctioning and need to be repaired.

    Now, if there was only a simple solution like that for my short game! :-P

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  35. Jack H says:

    Same as 29, or 5 either is correct. Anyone know if Cleveland will be coming out with a new set of irons for 2011.

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  36. Dan Murphree says:

    Number the machines 1 – 7. Take 1 coin from machine 1, 2 coins from machine 2, etc, up to 7 coins from machine 7. This should total 280 grams. The machine that is producing 9 gram coins will cause it to be 1 less than 280 times the number of that machine. So if the total is 277, the machine producing 9 gram coins is number 3.

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  37. Hoan Pham says:

    Label the machines and take the corresponding number of coins from the machines.

    Then take the 9 gram coins and use them as ball markers.

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  38. Cory says:

    Progressive sampling method it is. No need to repeat it. It would generate the correct answer (broken machine) each time. It would also work if you had one machine producing a heavier coin. Just got a new CG14 last week. Chipped two in so far through 2 rounds. Call it luck, call it confidence, call it what you will…I call it a sweet wedge. The CG14 could use a CG15 to buddy up with in the bag!

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  39. Bill Johnson says:

    I really like response number 2. I think I would do it that way as well.

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  40. Michael Bianco says:

    Take one coin from each machine, # them 1 – 7 and put them on a scale. They should weigh 269 grams. Remove one coin at a time, from the scale, until the last # of total weight is less then 9, such as 260, then you have you the broken machine. How many grams does a CG15 weigh? I would like to know, so when I replace my CG12 with the wedge that I win, will it change the weight balance of my bag.

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  41. Bradley H Lobdell says:

    Yeah, they got it right.

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  42. Russell Smith says:

    (no spam)

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  43. Rami says:

    Ok this was a good video. Though this guy has misstated a few tinhgs. First the top 4 grading companies should be PCGS, NGC, ANACS, AND ICGS. Second, a mint state coins is not a coin that has never been touched. A mint state starts off has coins with ware, but can have blemishes, scratches, and bag marks. Third, eBay is ok to use, just watch out for ratings, if they guarantee returns, and never buy from China

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