Hong Kong Elementary School Admission Test

Can you solve this in 20 seconds?  If not, perhaps you are like I not ready for the 1st grade.

Try it on your iPad or a Smart Phone, this could help:)

The answers are accepted any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon. 

Must See Movies

One friend is telling another:
- I am going to recommend you 5 movies each of which will completely turn your life upside-down.
One month later:
- Did you see my movies?
- Yes, I did.
- What do you think?
- Oh, I should have stopped after the ....

Your task is to complete the last sentence and provide the explanation to your answer.
This puzzle came from my co-worker Ira.

Your thoughts and suggestions are accepted any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon. 

A Simple Magic Square

Magic squares are tables of numbers where sums of every row, every column and both diagonals produce the same number. No, they were not invented by Ben Franklin, but have been around for thousands of years before. Take a look at this one on Gaudi’s Sagrada Família church in Barcelona:

Now, a little Magic Square puzzle suggested by our reader Lulu:

There is a 3 X 3 table with 9 cells in it and we are required to fill in the table with numbers from 1 to 9. Each number can be used only once. The numbers have to be placed in such a manner that they add up to 15 horizontally, vertically and diagonally. Can you do it?

Your thoughts and suggestions are accepted any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon. 

Read more about the history of Magic Squares and Sudoku here.

A puzzle that 99% will fail to answer.

This came from my son who got it from someone else at school. 

I solved it quickly and texted him the answer just as I was getting into my car for work. 

He wrote: "Wrong" and sent me a ridiculous solution.

I typed: "Ohh boy, how could you miss it!  I will beat you up at home:)" and started driving.

Stuck in traffic I thought back to it and the 99% that are getting it wrong and suddenly realized that his answer is in fact correct!

I texted: "Apology! Now that my head has cooled off I see that you were right."

He wrote: "Hahahahahaha".

No one at my work got it right either.  Could you?

There is at least two solutions. Let's call them: my and my son's. Both are kind of correct. But his is more original. 

Your thoughts and suggestions are accepted any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon.

The Question that 50% of the Harvard, Princeton and MIT students get wrong but you will solve.

This question is present in the century-old math books and is usually marked for the elementary school age.  Yet it is the question that get many adults confused. A question that one may fear to get on a job interview or an IQ test. A question where your tongue will compete with your logic. Where answering fast usually means answering wrong. Rumor goes around Facebook and email that 50% of the Harvard, Princeton and MIT students get the answer wrong.  But you surely can do this right:

At a candy store a gum and a candy cost $1.10.
Gum costs one dollar more than the candy.
How much does the candy cost?

Image by Bart Heird, distributed under CCL.

Your answers accepted any time until midnight on Sunday on our Family Puzzle Marathon. They will be hidden till then and everyone who submitted something reasonable will get a puzzle point.

A Simple Puzzle

Here is a puzzle that looks simple but I am not sure it is as easy at it seems. Feel free to ask your kids or parents to help you. It is "One age fits all" puzzle.  This puzzle is from a great book of Eye Popping Puzzles by Frank Coussement,Peter De Schepper and Keith Kay.

This stone piles are not random. There is a pattern. Can you figure it out and tell how many stones should be placed where the question mark is?

Your answers accepted any time until midnight on Sunday on our Family Puzzle Marathon. They will be hidden till then and everyone who submitted something reasonable will get a puzzle point.

A Matches Puzzle

This puzzle arrived via email from one of the fans. Can you move just one match to make this statement correct? There is more than one solution.

How can you answer? You can describe in words which match should be moved where to create what digit or sign. You can draw and email it directly to me. Unfortunately the blogger interface will not allow you to post images in the comments.
Good luck!

Your answers are accepted any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon.   

The Pyramid Curse

A few months ago my daughter received a letter from a friend that invited her to join a mail game. You buy a sheet of stickers and mail it to the first address on the list. You then copy the list, removing the first address and shifting the rest, adding yours as fifths at the end. Then you mail this list with instructions to 5 of your friends. Wait a few weeks and then expect hundreds if not thousands of stickers by mail.
5^5=3,125
Sounds mathematically correct.

Such examples of pyramid behavior are everywhere:

1. an avalanche
2. a viral email with good jokes, scary health advisory, slides of the weird asphalt painting, gorgeous sunsets (that by-the-way never comes to your email box once)

Getting back to the Pyramid games, such as the sticker game my daughter received.  We all tried it at some point in our lives and were surprised to find out that they usually do not work. While one math reason makes them attractive, another math reason prevents them from running smoothly. What is it?

Your answers are accepted any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon.

Die Hard because of St. Ives Riddle

This innocent riddle was a matter of life and death in the movie "Die Hard with a Vengeance" when protagonist had 30 seconds to solve it and then telephone the villain on the number "555 plus the riddle answer" or a bomb would detonate.

As I was going to St Ives
I met a man with seven wives
Every wife had seven sacks
Every sack had seven cats
Every cat had seven kits
Kits, cats, sacks, wives
How many were going to St Ives?

Can you solve it?

Answer ideas accepted any time until midnight on Saturday December 10th (EST), on our Family Puzzle Marathon. They will be hidden till then and everyone who submitted something reasonable will get a puzzle point.

Magical fragrance - how to share

Fairy god mother granted two of her favorite fairies a bottle of magical fragrance pictured below.  She commanded them to split the fragrance equally.  

As fairies were in a state of war with each other they were not keen on sharing the fragrance daily.  So they decided that one of them will use half of the fragrance and pass over the bottle with the remaining half to the second fairy.  The bottle is semitransparent but not symmetrical in either horizontal or vertical direction.  How can the second fairy verify whether the amount she gets is indeed half of the original amount?  The bottle was completely full to start with. No measuring marks are present on the bottle and fairy doesn't want to pour any drops of the magical liquid out.

Answer ideas accepted any time until midnight on Saturday October 22nd (EST), on our Family Puzzle Marathon. They will be hidden till then and everyone who submitted something reasonable will get a puzzle point.

Eight eights that are a thousand

This is an easy puzzle that you all are welcome to share with your kids and friends:
Put addition signs between the digits 88888888 to get 1000.

Answers accepted all day long on Friday April 8th, on our Family Puzzle Marathon. They will be hidden until Saturday morning (EST) and everyone who solved it will get a puzzle point. Please, explain your answer.

Lemonade Stand: a profitable enterprise?

With the first signs of spring and a T-shirt weather my daughter recollected her dream of placing a lemonade stand on the street. We have never done it before - our weekends are so packed with activities, and I (who grew up in a socialistic environment) am so uncomfortable selling anything to our dear neighbors. But I know that one day or another I have to let her live this simple dream. I am also certain that this could not be a powder-based lemonade that has that distinct chemical taste. We should go for the real thing. The question is: can this whole enterprise be profitable? I doubt that even my super nice neighbors will pay more than a $1.50 for a paper cup with a fresh home-made lemonade.

Here is a simple lemonade recipe I found on the web:

Ingredients
1 cup sugar
1 cup water (for the sugary syrup)
1 cup lemon juice
3 1/2 cups cold water (to dilute)

Assume that the water is free. Lemons are 3 for $1. It looks like we need approximately 5 lemons for 1 cup of lemon juice. Sugar is 2 pounds for $1.50.
9 oz plastic cups are sold 50 for $2.50.

Is it possible to make any profit with this enterprise?

Top image by Conlawprof, distributed under CCL.

Answers accepted all day long on Friday & Saturday, on our Family Puzzle Marathon. They will be hidden until Sunday morning (EST) and everyone who contributed something reasonable will get a puzzle point. Please, explain your answer.

New Kitchen Chairs

This puzzle celebrates our 20 puzzle point solver - Wang. It goes like this:
Wang and a friend have been shopping for new kitchen chairs. They went to a few stores, tried sitting on the wooden chairs, plastic chairs, aluminum chairs, counter stools and bar stools. To their surprise they found most of the four-legged chairs less stable than most of the three-legged chairs that they sat on. Wang has been contemplating about this all the way home and suddenly it occur ed to him that there is mathematical truth behind their empirical observation. What is it?

Top image by Fernando G., distributed under CCL.

Answers accepted all day long on Friday, on our Family Puzzle Marathon. They will be hidden until Saturday morning (EST) and everyone who contributed something reasonable will get a puzzle point. Please, explain your answer.

The Perfect Presents Puzzle

Image by triplezero, distributed under CCL.

You are going to visit your friend in Chicago for the winter Holidays and emailing her to find out the exact ages of each of her 3 children (all girls) to buy them presents. She is texting you back, but apparently distracted with the fever of her youngest daughter, all she writes is that she wants to talk to you about kindergarten for the next year. She also mentions that last night kids calculated that the product of their ages is equal to her age. You search on Facebook and see that she was born in May 1974. What are you to do about the presents? Is there any way to figure out her kids' ages?

Answers accepted all day long on Friday, on our Family Puzzle Marathon. They will be hidden until Saturday morning (EST) and everyone who solved correctly will get a puzzle point.

Unguarded Halloween Treats

Halloween evenings are exciting and busy. Your kids are dressed up way in advance and couldn't wait to start trick-o-treating. As soon as first darkness descends, you finally figure our your costume, and get to the streets to walk your kids from house to house making sure candy goes to the pumpkin and not straight into their mouth. But who will stay at home to give away your candy? You decide to leave the giant bowl of candy outside of your front steps. While trick-o-treating with your kids you noticed that this year there are twice as many little kids as older kids walking around. When you return in an hour, the bowl is empty. You are wondering how quickly all the 350 Kit-Kats have gone and how many kids may have stopped by. You are pretty sure little kids took one candy each as they were supervised by their parents. As for the older kids, you suspect that half of them may have snatched two candies. Can you estimate how many kids stopped by your house?

Playground Safety

Image by StormyDog

How do you know whether you kid will fit inside the slide or she/he is too tall for it?

Submit your answer on our Family Puzzle Marathon Be first to solve three puzzles and get a prize!

Just a Walk Around the Block

Image from Flickr

You go for a walk around the block with your daughter and. Two-thirds of the way, she stumbles, falls and gets a booboo. "Mommy, I have blood!" Some tears, some sobbing, some thumb sucking. You give your daughter a piggy-back ride the rest of the way and spend twice as much time on this little interval as you did while walking together. Father sees you approaching your home and says: "Hey, it looks like stuck on top of each other you are twice slower than walking side-by-side. I wonder how fast we'll go if I take both of you on my shoulders?" Is his estimation correct?

Submit your answer on our Family Puzzle Marathon Be first to solve three puzzles and get a prize!

The best deal on a plane ticket

Summer is a time of vacations and many of us have been or will be purchasing plane tickets for these long-dreamed-about trips. I usually look for a minimum number of stops, convenient hours, not too short and not too long a layover, and a familiar airline. Then, I go for the cheapest selection on this list. The difference between the least expensive choice and the next one is usually around 5%. That can be $50 for an International flight or $15 for domestic. Sounds like a good strategy, right? On my recent trip I was not so sure about that.
My least expensive choice didn't have personal TV screens in front of every seat, something that became very common on large planes and long international flights. On the way back, audio, light and even flight attendant buttons didn't work for the whole row of seats I was in. Toilets were dirty, food bad, flight attendants not very courteous. There were no eye cover and comfy socks that I know are being offered (or have been a year ago) on the airline that was next in price. Long-distance flights are never easy but for parents-flying-solo they can be rejuvenating: read, eat, watch, chat and sleep. Just yourself to worry about for a few hours or perhaps even a whole day. Quantifying all the things I expected but didn't get on my last trip, I am wondering whether this $50 difference was significant.

Perhaps I should adopt the same strategy as in a restaurant wine selection rule: pick second from the least expensive and you won't miss. What do you think?

Submit your answer on our Family Puzzle Marathon Be first to solve three puzzles and get a prize!

Enormous Lot

Over drinks in Vegas one Real Estate developer has been boasting about an enormous piece of land he got in Montana. According to the developer his land was in the shape of a triangle. One side of the triangle reached 200 miles from end to end. On each of the other two sides lot extended 100 miles from corner to corner. All of the listeners were impressed except for one. That woman merely laughed and said, "Why a lot of that size wouldn't even have to pay taxes where I come from."
Strangely enough, this woman was correct. How could this be so?

This puzzle is adapted from a book "Puzzle it out" by E. Richard & L. Churchill.

Submit your answer on our Family Puzzle Marathon Be first to solve three puzzles and get a prize!

Two Miners - a tribute to M.Gardner

These two miners come out from a coal mine at the end of their working day. One of them has his face covered in soot and the other one still has a perfectly clean face. They both glance at each other in the elevator bringing them back to the surface. When they get home, the one with the clean face cleanses himself thoroughly and the other one does not. Why?

This puzzle is from the Martin Gardner's "Aha!" book.
Submit your answer on our Family Puzzle Marathon Be first to solve three puzzles and get a prize!