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. 

A Nail Cutting Puzzle

One mom told me recently that she cuts about 100 nails weekly. All coming from her own family.
Four young kids and her own nails.
The math is going like that:
Five people times (10 hand nails+ 10 feet nails)  = 5 x 20 = 100

Counting this I started to appreciate my older kids' abilities to use the nail cutter themselves. My two-year old though is giving me a very hard time with every nail-cutting attempt. I have to catch her, sit her on my lap in front of a TV screen or capture her attention with ridiculous stories while carefully concentrating on her tiny hands and feet. And even then, her patience rarely lasts for more than 5 fingers.
I have heard that it is even harder with cats and dogs.

What is your nail math?
Do you have any advice on streamlining the process?

Image by GeoFx via Flickr, distributed under CCL.

Handcuff Your Kids

We are half-way through the summer vacation and you may be running out of ideas, resources and patience for how to entertain your kids while making sure their brains do not melt in front of screens, and they don't fight each other the rest of the time.  Here is a short trick that will show them who is the boss, force them to collaborate, yet will leave them giggling.

Handcuff your kids. Yes, you heard me well. Use two ropes. Make sure not to tie them too tight to their wrists.

Now, tell your kids that they are free as soon as they will figure out how to untangle the ropes. No scissors or knives allowed.  Let them hug and dance around each other for a while, then lead them to the solution that you can see here.

Who is Faster?

My kids love racing each other: on foot, bikes, roller skates or scooter.
They also love arguing: you are older, so you have to give me a headstart, your legs are longer, but you are lighter.
Well, my son is 13 and is 6'8", my daughter is 10 and is 4'9".
How can I help them decide who is faster, factoring their age and size?

Image by Shanti Knapp, distributed under CCL.

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

A Pacifier Puzzle

Why pacifiers are almost always magically fall nipple-side-up saving us from the need to wash them before sticking back into baby's mouth? Ok, sometimes we do suck them before giving it back to our treasures. That, by the way, is the healthiest wash of all according to the latest research.

Three of my daughter's not-so-favorite pacifiers on the carpet of (oh!) our hotel room. Her favorite pacifier unfortunately doesn't fall nipple-side-up and didn't participate in this staged experiment.
If this reminds you a buttered toast paradox - you are on the right way to the answer.

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

Lost Teeth Puzzle

Teeth is an important topic of discussion in our home. Our 12-year old son recently lost his tooth in ... a swimming pool. Our 9-year old daughter keeps counting her lost teeth, wiggly teeth and growing teeth.  Every few month she goes on an ice-cream diet because everything else just hurts too much when your wiggly tooth is hanging on a muscle thread. And our 1.5-years old finally got her first four teeth to cut and chew a grownup food but is drooling, sucking and crying while another one is growing.

My husband and I are doing pretty well with our teeth this year but this may very well be because our dentist died... and we haven't found a new one yet to tell us what is wrong with our teeth.

So, an easy puzzle for tooth owners of all ages.

My 10-year old daughter came to me telling that she was trying to count how many teeth she has lost overall.  But every time she counted she got a different number: 16, 17, 13, 15. She was asking what is the actual number of teeth she lost. Can you help her produce the best estimate from these numbers?

Image by Clintus McGintus, distributed under CCL.

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

Number Tricks for You and Your Kids

The first one is for you:
How do you write 5 inside 4?
Hint: The Pope...


The second one is for your kids:
It is a hidden numbers game. Click below to view The Math Mom's logo. In it we hid at least 10 numbers. Print the image and together with your kids find all the numbers. Highlight them in a different color and email a snapshot to me.

Solve either trick and get one puzzle point. Solve both and get two. Your answers are accepted any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon.

Your Personal Math Sentence

This is a great activity for the whole family.

My daughter brought it from school and challenged us all to make our own math sentences. She was very excited about it, I guess because it made math personal and playful.

Write your date of birth. 

Use digits in your date and math signs to come up with a math sentence. For kids it is easier because they have lots of 0s in their dates.

For example my daughter's dob is 4.5.2003

Math sentence she came up with:  5x4 + 3x0 =20

My dob is 5.28.1971 and I am thinking about my sentence.

Submit your personalized math sentence any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon.

Top image by millersjon, distributed under CCL.

A Party Weekend

I apologize for leaving you without a puzzle last weekend. I went away, joining my husband at a conference in the South of France and meeting our long-time friends from LA.  Friends we haven't seen for 12-18 years, friends that got married, had kids, some divorced. 

Image by Cayusa, distributed under CCL.

Bear with me, this leads to a puzzle, but I have to explain first. On this specific weekend, my husband and I found ourselves in the company of 4 men and 12 kids. The wives and ex-wives all went on a long planned weekend trip to Paris. As appropriate in such situations, the men tried to group together for survival.  They all met at the house of one of them in a countryside, they brought wine, cheeses, baguette and a lot of chocolate. They managed impressively well, with the older kids taking care of the younger, with everyone above age 10 parting till 2am and everyone having a great time.

There were 4 men, each a father of 3 kids.

One of them left two older kids at home and brought two friends of his daughter instead.

Among the kids there were 2 pairs of twins of different ages, each pair of the same gender.

One men was laughed at by his friends that his wife and he go to Greece and make kid on a different island each year. 

Two fathers had only boys.

For each pair of twins there was a kid of the same age but of opposite gender from another family.

You now have to sort kids by families.

There were:

a 3-year -old boy,

a 4-year-old boy ,

two 5-year-old boys, 

a 7-year -old girl,

two 11-year-old boys and one 11-yer-old girl, 

three 13-year-old girls and one 13-year-old boy.

I do not use actual photographs for privacy reasons; the image above is just for illustration and should not be used as a hint.  So, who brought what kids?

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

The Fourth Wheel

A few days ago I went for a walk with my baby daughter. To be more precise I had an errand in town 30 min walking distance from our home. Slowly pushing the bulky stroller, I reached the destination, accomplished the errand and already quite tired turned back toward home. Just as I was crossing the street one of my stroller's wheels broke off and fell on the ground.
My first thought was lifting the stroller with the baby, grabbing everything into my hands and running away from the street. But I am no giant. Then, I tucked the fallen wheel in the stroller basket and tried pushing the stroller. To my amazement, it worked. The stroller rolled on the 3 remaining wheels almost as good (or almost as bad) as it was on 4 wheels. Two wheels were on the left and only one on the right - the back one. It looked strange not only to me. A few passer-byes looked in surprise and made sure I know that one wheel is missing. But we reached home in the same 30 min we walked there and my daughter managed to fall asleep along the way.  My question is, how is it possible for a 4--wheel creation to continue functioning even when one wheel is missing. Think about it - car requires a jack and will lean in one corner if one wheel is missing. A dog with 3 legs wont go far...So why did my stroller ?

I didn't get a picture of a stroller with the broken wheel. Here is the stroller, with all 4 wheels on.
Your answers are accepted any time until midnight Eastern Time on Sunday, on our Family Puzzle Marathon.    

Charger Fight

We gave our old iPhones to our kids this year, and got ourselves new ones through a deal with the provider. Now, in the quarto iPhone household we have constant fights over who gets to charge first.  We do have enough chargers but some of them are located in more convenient places than others: kitchen and car chargers are the most popular.

The other day our son gets into a car and screams in panic that he has only 40% battery left and needs the charger while my phone that is 20% full has just been plugged in. The truth is on my side, right?  But the problem is not as simple.  His older iPhone is losing power much faster than my iPhone 4G, even when they run idle. On average it takes his phone 2.5 days to run out of battery while for my phone it is 6 days. So, who deserves the charger?

Image by Sixth Lie, distributed under CCL.

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.

Pampers vs. Huggies

It has been 8 long years since we had a baby in the house, and transitioning along with our older kids we had completely forgotten all the baby nuances. One of them is how to avoid diaper changing in the middle of the night. It wakes you up, it wakes the baby up, the transition out from the cuddly warm blanket to the wet wipe on the baby's bare body in a cold room is a torture, it wakes your partner up, as well as the neighbors. Yet, the Huggies diapers that I purchased started to leak after 4 hours, making it impossible not to change in the middle of the night.

Is there any trick? I couldn't remember from my younger kids' days. I emailed my sister-in-law who recently had twins and all she replied was: "ONLY PAMPERS!!!!!"

Could it be so simple? I checked online and saw similar laconic advices everywhere on babies' forums.

I went to the store and bought the recommended brand.  Surprisingly they were exactly the same price as Huggies, like no one was in onto the secret.  We used it and, true enough, it doesn't seem to leak for 8-9 hours.

I know that more frequent diaper changes during the day is healthier, but for the night - the problem is solved. The question is: assuming that you leave a Pampers diaper on during the day for 4 hours and during the night for 8 hours, how much money you are saving as compared with Huggies diapers that you would replace every 4 hours night and day.  Let's compute it as a percentage of a diaper's price or assume that diapers are 3 for a $1.

Top image by dhinivh, distributed under CCL.

Answer ideas accepted any time until midnight on Sunday December 18th (EST), on our Family Puzzle Marathon. They will be hidden till then and everyone who submitted something reasonable will get a puzzle point.

Are you ready for the 7th grade?

This puzzle arrived from Kim, our expert puzzle solver.  It was on her 7^th grader’s last math test:

Add grouping marks (parentheses and/or absolute value symbols) to the following to make the equation true:

   -4  +   -8   + 2   *   6  ÷   -6   + 2   + 5   =   2

You are allowed to ask for your kids' help

Answer ideas accepted any time until midnight on Saturday November 12th (EST), on our Family Puzzle Marathon. They will be hidden till then and everyone who submitted something reasonable will get a puzzle point.

Top image by woodleywonderworks, distributed under CCL.

The magic with any three-digit number

My daughter's school teacher is showing kids some number mysticism.
She told them to take any 3 digit number, e.g.793.
Scramble its digits, e.g. 397.
Subtract from the larger of these two numbers the smaller one: 793-397=396.
Add the digits of the remaining number, e.g. for a number 396 a sum of digits will be 3+9+6=18.
Then, continue adding digits of the last number you got till the sum is just one digit: 1+8=9.
Surprisingly, no matter what number you start from and how you scramble it, the result is always 9!

The puzzle is why is this happening. And the extra credit question is how to explain this to a 8 year old.

Top image by Hryck, distributed under CCL.

Answers accepted all day long on Friday June 17th and Saturday June 18th, on our Family Puzzle Marathon. They will be hidden until Sunday morning (EST) and everyone who solved it will get a puzzle point.

Mysterious Pattern

After the April break a mysterious drawing has been discovered on the asphalt behind the school.



Was it an illiterate toddler, an artistic child, an infatuated teenager, or an adult trying to communicate with the aliens? After careful observation, one second grader screamed: "Wait, I see a pattern!"

What is this pattern?
You can submit your word description of the pattern via the comment form below or feel free to email me the snapshots of your drawings.

Thank you to our friend Peter Tze for sharing this nice puzzle.
Answers accepted all day long on Friday May 20th and Saturday May 21st, on our Family Puzzle Marathon. They will be hidden until Sunday 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.

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.

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!

Airport Games

Imagine that you are stuck in the Newark Airport because of a silly security breach or thunderstorms and you are going out of your way keeping your kids awake and entertained for a few extra hours. Their favorite thing to do is go back and forth on the moving walkway. Your daughter is daring you to a race. She says: "Let's see who is faster: you going ALONGSIDE the walkway all the way to the end and then coming back, or me going ON the moving walkway first time in the direction of the motion and then back, against the direction of the motion. I will try to keep the same speed both ways." You are tired and frustrated because of the delay, but you are a parent. So, you agree. Who do you think is going to win?

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