6 October 2025

What does “SOS” stand for?

Here is one of the interesting things I learned while picking up Morse code. I can’t believe I have lived all my life without realizing this.

What does the term “SOS” stand for? Growing up, I always thought that it stood for “Save Our Souls”. I believe I first heard this while reading about the story of the Titanic. Some think of it as “Save Our Ship”.

It turns out that “SOS” is not an abbreviation at all. About 75 years after Morse code was created, around the start of the 1900s, the Germans helped set a universal distress code: SOS. They chose it because its Morse pattern [… — …] was easy to recognize. Before SOS, other distress signals were used, with “CQD” being the most common.

So, SOS does not stand for any English phrase. And even if it did stand for something, it would have been very likely a German phrase!

Did you know that?

Category: Puzzles | LEAVE A COMMENT
22 August 2025

Why is my math not matching with ChatGPT?

I was driving back from the airport when I got a call from my old buddy SK and his son. Apparently, they were stuck on a math problem. What I understood is this:

SK’s son and his friend are trying to get two tickets to a concert. (He told me the name of the concert but of course, that was all Greek to me). The organizers are opening 50,000 slots you can apply to. And they will pick 4,500 of them as winners. In other words, there are only 4,500 seats available.

SK’s son and his friend bought 25 slots.

Question was what is the probability that the two friends would be able to go to the concert?

Apparently ChatGPT was saying 90%. SK’s intuition was far lower than that. His son felt that it made sense. So, over the phone we worked out the approach and agreed it will be a high number.

I got a message yesterday from SK that his son and his friend are indeed going to the show!

This early morning, curiosity got the better of me and I sat down with paper and pen to figure out what the probability would be.

Now, I am stumped! My answer is very different from what SK and his son reported as ChatGPT’s response was.

What do you think is the probability?

Answer published here

Category: Puzzles | LEAVE A COMMENT
18 August 2025

Triangle and 9 digits puzzle

This puzzle comes from my good friend Amrith.

Fill the three vertices and two spots on each side of the triangle with the numbers 1 thru 9 (using each only once) such that each side adds up to 20.

Multiple solutions are possible.

What approach did you use (other than simple trial and error)?

Answer posted here: https://www.rajibroy.com/2025/08/22/answer-to-triangle-and-9-digits/

21 June 2025

Can somebody help me with this simple math problem?

I thought it to be a fairly simple problem. Now I am stuck. I was reading a book that talked about organizational efficiency. It talked about 3 parameters. Each parameters can take the value of 1 thru 10. So, there are 1000 combinations.

It is at this point, I got totally distracted. The quick thought that came to me mind was how many different products can I get? And ever since, the book be darned, I cannot get my mind off it.

So, to repeat, there are three spots. You can fill each one of them with a number 1-10. So, you get 1000 possibilities. If you take the product of those 1000 possibilities, you will get 1000 numbers. But there will be repeats. For example,(1,2,3) (1,3,2) (2,3,1) (2,1,3) (3,2,1) (3,1,2) (1,1,6) (1,6,1) (6,1,1) will all give 6 as the product.

How many distinct products can you have?

11 June 2025

Vexillology quiz

These days, I have found a great way to learn more about country flags. My friend in office – Danny – is a wizard at this. He asks me questions. I get stumped and then I learn. I come home and learn a few more countries and go back and ask him next day. He answers them without even blinking. My upside is that in the process, I am learning!!

There is another friend of mine Sharmistha – in Houston – who is equally adept in world flags!

Someday, I am going to be like them. Right now I am grinding thru it – one flag at a time…

Here are some interesting things I have learnt…

1. Most all flags are rectangles. However, 2 countries have square flags. Can you name them?

2. Here might be something most people know. Which country has a flag that is neither rectangle nor square?

3. What is the most common color in all the country flags? It is found in a whopping 75%+ flags!

4. What is the most rare color in country flags? How many countries have them?

5. Which country has had the most number of flags?

6. What was the least amount of time that a country flag survived before it was substituted?

7. Which country has the oldest continuously used flag? Celebrating 400 years this year, in fact!

8. How many countries have the front side and the reverse side of the flag different from each other?

9. In the 1936 Summer Olympics, two countries showed up to compete and realized they have the same flag! Next year one of them made an alteration to their flag. Which two countries were these?

10. Many countries have images of arms – often symbolising their struggle and sacrifice for independence. Saudi Arabia’s for example, has a sword. But there is one country that has a AK-47 on its flag!! Can you name it?

Answers posted here.

9 March 2025

Puzzle for this Sunday morning

Take 18 matchsticks and arrange them to form the number 508. I realized that we do not have matchsticks in our home and certainly, we do not have 18 gaslighters – so, resorted to powerpoint to make the picture.

Now, the question is by repositioning two sticks (any two sticks of your choice), what is the highest number you can get? Post your answer in the comments section.

7 March 2025

Help!! A day later, I still do not have a solution

This is the Wordle problem from yesterday. I tried my usual first word. And hit jackpot with the second word. Got all the five letters but none of them were in the right position.

Then I got distracted. Instead of solving the Wordle problem, my idiotic brain converted it into a math problem. The question I had for myself was – in how many ways can I arrange the five letters (there is no repeat) where none of the letters will occupy the same position as the all yellow row. In other words, how many combinations of LATER can you come up with where the first letter is not L and second letter is not A and …. (you get the drift).

It is MUCH harder than I thought. One hour later, I realized I was getting late for office. Quickly solved the Wordle part and wrote to my nephew in UC Riverside before getting ready for work.

We still do not have an elegant solution. In desperation, I enumerated all possibilities. I have the answer now but do not know how to solve it.

HELP!!

16 December 2024

Geography quiz on land borders

This time the questions are about land borders between countries. See how many you can answer from what you know, remember or even guess before you resort to Google.

1. Which country has the maximum number of countries with who they have land borders? (Hint: there are 2 of them)

2. Of the number of land borders a country can have, what is the most frequent? (e.g. if 13 countries have 3 as number of land bordering countries, 17 have 4, 20 have 5 and there were no other countries in the world – then 5 would be the answer). [Hint: the answer is fairly surprising]

3. We all know that USA and Canada have the longest land boundary (and one that is not guarded by military too!). Can you name the other 4 in the Top 5? [Hint: Russia and China border is NOT one of them!]

4. Which countries have the shortest land border between them? [Hint: It is about 500 feet!!]

5. This one is also very unintuitive. A country can have multiple land borders with the same country. Enclaves or oblasts are great examples of that. Which two countries have the most number of separate land boundaries between them?

Answers posted here.