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2015-02-25

An interesting fact about me (not!)

For some reason, there is only one interesting fact about me that I can tell others and actually believe that it is true about myself.

This is the interesting fact: I can tell you whether a 3-digit number is a prime number (almost) instantly using mental arithmetic.

In hindsight, it's actually not really that interesting or unusual, if you consider the following:

(Warning: long technical, mathematical read ahead!)

Prime numbers are numbers which are divisible only by itself and the number 1. As an example, single-digit prime numbers are 2, 3, 5 and 7 while two-digit prime numbers are 29, 37 and 73.

Now, consider the total number of 3-digit number from 100-999. That is 900 numbers in total.

For any of the numbers in this range to qualify as a prime number, it cannot be
  • even, or 
  • end with the digit 5.
This in itself, already omits 60% of those 900 numbers which leaves you with 40% x 900 = 360 odd numbers. Thus, we only consider odd numbers for possible prime numbers.

Certain odd numbers have patterns which immediately excludes itself from the prime numbers list. Some numbers include the 'divisible by 11' odd numbers which are 121, 363 and 847. Others include the 'triple' numbers such as 111,333,555, 777 and 999.
We have shortened the list of possible prime numbers by another 8, bringing it down to 352 odd numbers left to consider.

Sequential-pattern numbers like 123, 567, 987, 321 and 789, or even 357, 753 or 147, 741 & 369, are always divisible by 3.
Another set which cannot be prime numbers are if each of the three digits in the 3-digit number is divisible by 3, such as 339, 663, 660 and 993. This brings the prime-number pool down even further.

Furthermore, if you are good with your 3- or 7- times table, doing division should be a breeze, and hence, if given an odd 3-digit which do not fall in any of the above categories, you are able to narrow down the list of  possible prime numbers further by doing quick mental division using 3 or 7 which would not be a prime number if it leaves no remainder.

Now, the next step which has an increased complexity involves division with double-digit numbers, which is indeed much more difficult to do compared with single-digit numbers. However, based on the primality test, a number n can be tested for primality (the characteristic of being a prime number) by dividing using all possible numbers up to the number √n. 
For example, the number 391. No single digit odd number can divide this number perfectly. Hence, we must try double-digit numbers from the number 13 (ignore using 11 as 391 is definitely not a product of 11). To test for primality, we need only use the odd prime numbers 13, 17, 19, etc. up till √n, or √391 in this case. But of course, it would defeat the purpose of using mental arithmetic if one uses a calculator to compute √391 and thus we would be at a loss. However, we can use approximation to find the value of √391, in which the closest perfect square to 391 is 400, which has a square root of 20. Hence, we need only use 13, 17 or 19 to determine if 391 is a prime number or not.
Yes, this indeed seems complex. By the way, as it turns out, 391 is a product of 17 x 23, hence NOT a prime number.

Ok, brain is in knots now you may say. :S !!!

The point of all this is to illustrate how few numbers there are in the pool of 3-digit prime numbers. The exact total is actually a mere 143 prime numbers, which is moderately easy to commit to memory.

Which brings me back to the point I was trying to make at the start of this post, that is I merely memorised a pool of 143 prime numbers; this is how I can instantly tell you if it is a prime number or not.

Now, not all that impressive anymore, ain't it? Haha.
Why I so long-winded must write so long just to say my 'talent' not very interesting after all, LOL.

But some historical fact about me regarding this 'prime number talent' is that it all started on a school bus, as a little girl on her way to school. She was always the earliest to be picked up and the last to be dropped off, hence having ample time doing nothing while on her commute to and from school. This little girl eventually learnt how to multiply and divide, opening up more 'mathematical' possibilities, which was harnessed during her commute to school. To dispel boredom on these dreaded long rides to and from school, she found that you could play arithmetic games using car number plates which can be seen everywhere while on the bus.
This is how that little girl (me) learnt and eventually memorising 3-digit numbers, whether prime number or not, and even 3-digit perfect squares.

Oh well, I guess I can still impress those who regard prime numbers as 'foreign' and 'hard to figure out' (and those who haven't read this post) !!!!


Some good words from a newspaper 'Opinions' section

With the ubiquity of the Internet and social media, information flows freely and it is easy to get a tiny bit of knowledge about many things. What is dangerous is when people assume their knowledge gives them credibility, and then ignore newer, contradictory information because it challenges their belief

2015-01-28

Of Service Matters

I suddenly have this urge to write about the services I received yesterday to settle my mum's new phone.

Yes, I think we all have experienced something similar: rude, unfriendly, arrogant customer service, and at the other end of the (good) spectrum, really friendly and courteous service.

Well, for this rant, it will include both types as aforementioned. Here goes.


1. Changing SIM card
About mum's new phone, she recently purchased the Samsung Galaxy A5, a recently launched model, which she is transitioning from her more 'inferior' Samsung Ace Plus. So it required the change of the SIM card to a nano sim. Hence, a visit to her mobile operator DiGi was required.
One 'notorious' fact about service centres in Malaysia is that, they are almost always full (perhaps this is true all over the world -__-"). This inadvertently means that waiting lines are long. But that's fair, since there aren't enough service centres anyway -__-".
So anyway, fast forward to when we received service, the lady was friendly, and so was the guy, who was quite impressed with the phone as he used to work at Samsung. I like that they had a smile on their faces and were patient with my queries, and even struck up a conversation on Samsung phones. No hassles encountered at all during the change of SIM card. I give them a 5/5 for customer service :)

2, Screen protector
So, this phone was bought from another shop about a week back, from a phone wholesaler. Unfortunately, at the time of purchase, they did not have the screen protector in stock for this model, so instead, I bought two sets of it online. However, I screwed up the 'installation' of one of this screen protector on my mum's phone, because the more I tried, the more air bubbles formed underneath -__-". So mum decided to take the second (and last) one and ask a kind soul from any mobile phone shop to help us install it (for free). I argued saying that, who would do it for free? You're not even buying anything from them and you want them to do it for you for free? Then mum relented and said, "Oklah, I'll just get the screen protector from them".

And that's what we did.

We decided to try the Samsung shop first and see if they'll do it for free since the phone is Samsung, there's at least some sense of  'relation' to the phone, despite it being an irrelevant screen protector. Well, that was my rationale at least. So let me give to you (somewhat verbatim) of what went down once I entered the Samsung shop:

Me: Hi, I have here a Samsung A5 (I emphasised the word Samsung). Do you think you can help me install my screen protector (I showed him my screen protector)? It's a Samsung A5 (I repeated just to get the idea across that it is a SAMSUNG phone!)
Guy: Oh sorry, we don't do that.
Me: Well, it's a just a screen protector.
Guy: No, we don't do.
Mum: Ok, we'll pay you some money to help us put it on, since we are really not good at this.
Guy: No cannot. We don't help people put.
Me: How much is your screen protector? *sounding annoyed*
Guy: RM99
Me: Wah, so expensive??? *purposefully saying in very annoyed tone.. RM99 is stupidly expensive okay >:(*
Guy: *blank face*
Mum: Even though it's Samsung phone, you won't help us put? I will pay you some money lah.
Guy: But this phone you also where got buy from our shop?!
Mum: Huh, like that one ah. Oklah, thank you.
Me: Mummy, don't even bother saying thank you lah. *but my back was already facing the seller*

Wah, I tell you, the moment I walked out of that shop, I wanted to swear vulgarities at this pompous ass of a salesperson. But I refrained because I had to be the better man. Ugh,

Service rendered: -0.5/5. Negative 'cos you are a bad salesperson.

To give him some credit, he wasn't rude... until the "This phone you also didn't buy from our shop?!" remark. The audacity some people have to say the most 'defensive' things to not help someone is quite repulsive.

Why are people so quick to make such overly-defensive statements? I mean.. What are you even defending yourself against? I'm not even attacking you, I'm asking you nicely and you in return rudely make such a statement. Which I think is not even a fair argument. Here's what he could have said instead:

"Sorry, we only help install if you buy the screen protector from our store. It's company policy" -- maybe his English very bad. But seriously? He really didn't think of saying anything else, except answer our questions with  a very rigid "No, we don't do that."? How very limited in thinking is that?
Seriously, sales people should know better. Furthermore, he looks older than me, so he should have had more experience dealing with customers than I would. Dude, come on, sales people should be talking more than their customers. Not a short "Yes" or "No". You're not a damn private in the military.

For one:
-I'm offering to pay you to do it, which translates to extra income for you.
-You practically have nobody in the shop at the time, and what were you doing when I was walking in? Playing with phone. Isn't that more unethical in the context of work ethics?
-Even if someone were to walk in the shop at the time, your two other colleagues could attend to them, while you could be helping us install the screen protector.

So yeah, pretty much a very typical rigid type of Malaysian thinking and behaviour that pervades the customer service industry. It's really sad and paints a really bad picture of our country.
But one thought popped into my mind... if a really hot and sexy chick walks in asking for his help, and if he f*cking said yes to the same request from her instead, I swear, I'll get his name and write a really bad review of that shop. I hate f*cking double standards especially when it's so superficial.


3. Another shop
So we walked out, and so happened there was a non-brand specific mobile phone shop just a few steps away. We tried again, but this time we first asked to buy the screen protector from their shop. Exchange as below:

Girl: Yes, can I help you? What do you want to buy? (BINGO! Customer Service Etiquette#1 - CHECK.)
Me: Do you sell this model's screen protector?
Girl: Oh, this one no.
Me: Oh, okay. We have our screen protector, but can you help us put?
Girl: *asks her immediate boss at counter* Can help ah?
Boss: *thinking* Oklah. (Customer Service Etiquette#2 - CHECK.)
Boss: *takes phone and looks* Good ah this phone?
Me: Not bad ah.
Boss: *turns on screen, and inspects the body* Wah, nice colour ah, and the body also so slim.
Me: Yeah, nice hor. You got sell ah?
Boss: No wor. *proceeds to put s.p. on while we observe her deft hands doing it*

-- she was doing it like it was just another paying customer wanting to have a screen protector on their phone. No discrimination, just pure and simple work-as-usual. Customer Service Etiquette#3 - CHECK.

Boss: Ok, done.
Me and Mum: Thank you, wah so nice!

Then, I gave her the RM5 I had in my hand. She rejected it, saying "No lah, no lah, it's ok"
But I put it in her hand anyway and thanked her again.

Now, you see, she exemplifies a kind soul. She volunteered to do it for free, but surprised by the offer of payment. Come on, RM5 for 5 minutes of work is welcomed anytime if it were me too! The as*hole guy in the Samsung shop sure didn't think of that for himself. Pffffffft.



So, that's pretty much it for one night's urban adventure. I just think that offering a helping hand, especially when it means so little on your part, should be offered without even thinking twice if asked.
If someone ask you to open the door for them, wouldn't you do it?
If it's to turn on something that you know how to, why not help?

It's not about the money... it's about courtesy, small help, paying-it-forward type of altruism.
I guess there is hope after all when I went to the second shop. :)







2014-12-06

Things you should know as you get older #6

One certainty about growing older is that you grow wrinkles, and not necessarily wiser.

2014-11-09

A Timeless Song for Always

This is a classic from the rock genre, a hit I will always love.
Bon Jovi, Always (1994)
This was also the years men sport long flowy hair.
Gotta love the 90s.

2014-10-27

Here's a sentence I found

Stumbled upon something that triggered reading about the Iranian Revolution of 1979 which toppled the last Shah of Iran from his monarchy in place of a new Supreme Leader  which is (till today) governed by an Islamic theocracy.

It was this sentence that made a lot of sense about 'brain-washing' and 'blind-siding' :

Revolutions, Islamic and otherwise, seldom deliver on all their promises, and a clear external enemy can serve as a useful diversion from internal problems.
Think North Korea too.

Familiar? Well, I don't know, I'm probably another cog in the wheel. But when many of these cogs decide to stop working (and start revolting) in the tangible yet invisible machine that they supposedly serve, things can go.... awry.

You know the saying "No news is good news."; to be frank, we could all use a little more of this absence of bullsh*t. I'd prefer it more than anything in my daily dose of reading.