Today’s puzzle has a special extra. Because the problem is geometric in nature, I thought it would be fun to make a video of the puzzle on Youtube.

Here is a link to the puzzle videos on Youtube.

Efficient drink order problem – Youtube (it’s just over at minute at 1 min 18 sec)

Solution to efficient order drink problem – Youtube (it’s a bit longer at 3 minutes)

As they are my first videos on Youtube, they are a bit plain. Still, I put a lot of work into them and any feedback would be much appreciated.

For those who prefer the normal format, I’ve also included the normal text-only version of the puzzle after the jump.
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The last time I was at a local Target store, I noticed something strange. At the end of the cereal aisle, there was a display rack for batteries. Not something complementary like snack bars, or nuts, or hot chocolate mix. The rack had batteries, hundreds of packs of disposable batteries of all sizes.

I mean who is shopping for cereal and suddenly decides to buy batteries? Why would Target put such an unrelated item next to cereal?

In fact, as I walked around the store, this was not the only place that Target was racking batteries. It made me suspect something more was going on.

(On an unrelated note: I was interviewed over at Just Tap the Glass by Kene Erike. Check it out: interview at Just Tap the Glass)

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Do you buy things because you can really afford them, or because you see people poorer than you have bought those things?

We are influenced by how others spend, and a recent paper documented how social status can affect our spending.

From the press release at the Journal of Consumer Research:

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If you go around asking for free things, you will occasionally get lucky. But if you habitually bother people, you will be labeled as a pest and your luck will run out.

That’s why it pays to be more subtle in your requests. This post is about a negotiating technique that can help you get free things, without being too obvious to the other side.

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Golden Balls is an amusing British game show. Especially interesting is the final contest which is a version of the Prisoner’s Dilemma.

If you’re never seen the show, here is how it works. Each of two contestants independently chooses to split or steal the final prize. If both choose split, then the prize is divided evenly. If one chooses split and the other steal, the person who steals gets the entire prize. If both choose steal, however, then both walk away with nothing.

Here’s the normal form representation of the game:

How should you play this game?

One contestant had an amazingly brilliant strategy that I will discuss below.

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I’m excited to announce that my first ebook is on sale.

It’s plainly titled Math Puzzles: classic riddles in counting, geometry, probability, and game theory.

Buy at Gumroad: https://gumroad.com/l/pjHS

The ebook costs $4.99 and it contains 70 of the best puzzles from the Monday puzzle series. The link above will take you to a website Gumroad where you can pay for the book by credit card. You’ll immediately get a link to download the ebook, and you will also get a copy by email just in case.

This is the first time I’m selling an ebook, so if there are any hitches, please email me immediately (presh@mindyourdecisions.com) and I’ll be happy to solve the problem.

Very important: I should mention the ebook does not contain any new puzzles, so don’t buy it if you’re expecting new puzzles.

That said, the ebook is nice way to read these puzzles, and it would make a perfect gift for anyone who loves math.

Want a free copy?

If you run a reasonably sized blog, I’d be happy to send you a free copy. I would ask you post a review on your blog with your honest opinion. I’m also happy to do interviews over email.

Email me if you’re interested: presh@mindyourdecisions.com

Coming soon: Kindle and other versions

Personally I prefer ebooks in pdf format with no DRM. I am guessing you guys would feel the same way, so that’s why I decided to go with direct distribution.

That said, many people prefer to buy things from Amazon and other marketplaces, so soon the ebook will be available for the Kindle and other ebook readers too.

Thanks for all your support!

This part is going to sound sappy, but it’s something I really want to say.

I’ve been writing this blog for nearly 5 years now, and I have to thank you all for all you’ve done. The feedback through email, comments, and shared posts has been amazing and has kept me motivated to keep writing more.

This ebook would never have been possible without all of that support.

Let’s play a game of chance.

I have in my hand a standard 52 card deck. What I will do is flip over two cards at a time.

If the two cards happen to be red, then you get the pair. If the two cards are black, then I get the pair. If the two cards are different colors, the pair of cards is discarded.

I will continue flipping the cards until the entire deck is dealt.

At the end, you and I will have some pairs of cards. If you end up with more pairs, then lucky you, I will pay you $10 for every extra pair you have. If you have fewer pairs than me, then you just lose the game and walk away.

The game costs $1 to play. Are you willing to try your luck?

Think about it before reading the answer after the jump.
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Dark Lord Imperial Stout is one of the most highly rated and desired craft beers. The market for Dark Lord is especially interesting because its supply is very restricted.

Dark Lord is only distributed on one day of the year in a festival known as Dark Lord Day.

While festival tickets cost about $20, it is even hard to buy tickets. The ticketing website is always overloaded, and only a lucky few can get the tickets.

The extreme demand and limited supply create a lively market for resale of the Dark Lord beer, and even for tickets to the Dark Lord Day festival, which entitles one to buy the beer.

Tickets for the festival alone can run $160 on StubHub and eBay. This seems outrageous to many as this is just a ticket for the festival with a right to buy the beer.

Still, could the $160 price be justified? I think it can, if you consider the economics.

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I had a hard time accepting that skydiving could ever be considered a low-risk activity. Call me old fashioned, but it just doesn’t seem prudent to be jumping out of an airplane with a parachute as your life support.

But however I feel personally doesn’t really matter. I’m happy to judge the risk of skydiving objectively using cold, hard statistics.

In this regard, skydiving has an impressive safety record. Some have even gone so far to say that skydiving is safer than driving. But can that really be the case?

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I saw an ad for Capital One’s Venture card that got me curious. The ad stated the Venture card offers much better rewards than other cards offering miles, and it was named as one of Money Magazine’s best credit cards.

That claim naturally got me skeptical, so I dug into the math to see if the Venture card really delivered rewards.

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A father bequeaths a triangular piece of land to his children, Alice and Bob.

The father was known to be quirky, and in his will, he specified a rather unusual way for the land to be divided.

On a map of the land, Bob is to mark a location of his choosing. Then Alice gets to mark a location.

Bob will be given all the land that is closer to his marker than Alice’s, and Alice will own the rest of the land.

Assume the land is an equilateral triangle. Which child is favored in this game, if the goal is to get the most land?

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The Excel function rand() generates a random number between 0 and 1.

Let’s say I generate two numbers using the rand() function.

What is the probability the two numbers sum is less than 1 AND their product is less than 3/16?

Give it a try, or experiment numerically, before reading the answer after the jump.
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Most American theaters sell movie tickets at a fixed price. There usually are discounts for early showings or for child/senior citizens, along with a premium rate for a 3D movie, but that’s pretty much it.

In Pune, India I noticed a much more tiered pricing system for its movies.

Here’s an example in which a theater set ELEVEN different price points for a single movie.

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The hotel I was staying at had an interesting kiosk in its lobby.

The kiosk offered internet access for anyone that wanted to browse the net, check email, or print out boarding passes.

It also seemed to have reasonable prices. The kiosk said you could browse the internet at $0.25 per minute and print at the rate of $0.50 per page.

Those prices sounded reasonable, until I read all the terms on the kiosk.

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Three months have already gone by this year. How are you keeping up with your financial goals and New Year’s Resolutions?

Now is a good time to evaluate if you have been keeping up with your budget and spending plans. If you are spending too much, you have enough time left in the year to balance things out. If you have a surplus, you can plan for a summer vacation or add to your rainy day/emergency fund.

Here are a few ways you can review your quarterly spending in my free expense tracker and budgeting spreadsheet (download the latest version here).

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