Money

Future job comparison

Posted July 30th, 2008 by Mgccl
in

Data From Salary.com

Y axis is amount of money in dollars
X axis is the percentile, only plot 3 points, 25th, 75th and 90th.
A line with the lowest starting point in each color means Instructor of [Insert Major].
2nd lowest is Assistant professor of [Insert Major].
3rd lowest is Associate professor of [Insert Major].
then it's Professor of [Insert Major].
Last one is Dean of [Insert Major].

From what I can see, clearly, the safe major to chose is computer science. Pay is good even for a CS instructor(around the same pay as a associate professor in philosophy, damn!

Philosophy is the most unsafe. Unless one can become a professor and manage to get into the very top, it's better to select the other 2.

Math is good. Money increase is steady compare to title.
Math professors can earn more than dean of mathematics.

Dean of medicine totally owns everyone else in colleges. The 25th percentile is already outside this graph.(almost 300K)

Amazon 4-for-3 deals

Posted July 25th, 2008 by Mgccl
in

Amazon 4-for-3 deal:
Buy 4 item and have the one with the least price free. 4-for-3 items are under $10.
I believe if I buy 4n books, then it will be made into a 4n-for-3n deal that's not in writing, where n items with the least price is free. I did not test it yet, hope someone try that for me. Maxium saving is 25%, not bad.

How to maximize the amount of saving, suppose there is no such thing as shipping fee(If you are in your Amazon prime trial period).

1. Assume one have to buy n items.
2. If n is divisible by 4, the best strategy is to sort the items by price, forms a series of prices a_i, where a_i\le a_{i+1}. This also forms set B.(uhh.. this set allows repetition of elements...)
3. Buy a vector of them each time <a_{4i+1}, a_{4i+2}, a_{4i+3}, a_{4i+4}> for 0\le i\le \frac{n}{4}-1, which will maximize saving.
Proof: The total amount of money paid for this method is
\sum _{i=1}^{n} a_i - \sum _{i=0}^{\frac{n}{4}-1} a_{4i+1}
Make each of the number removed into a set, S
Each time find one element for S, the 4 element of B is removed.
A non-rigorous proof
Create n blocks out of 4n elements in B, name it b_1,b_2,b_3.....b_n
S is set containing the minimal for each b_n.
we can see a_1 has to be part of S, and b_1.
suppose a_2 is not in b_1, but in b_k,
and a_i is the smallest number in b_1 other than a_i.
If one switch a_2 with a_i, we can find all the smallest number in b_k is larger than a_2. All the rest blocks doesn't change at all.
Which shows that a_2 must be in the same block with a_1 to allow the sum of S be maximized.
use the same reasoning for a_3 and a_4.
and use the same reasoning for all blocks.
we get the original way have to be the best way.
If the count of elements in B is not divisible by 4, the best way is still the same, group items of 4 from most expensive to least expensive, remain a few least expensive ones in one group, buy each group separately.

This can be extended to any n-for-n-1 deals and should be able to extend to any n-for-k deals, where k lesser than n.

First unauthorized charge on my credit card

Posted March 31st, 2008 by Mgccl
in

Freecreditreport.com claim to give free credit reports to people.
They do, btw they also sign you up for their "CIC TripleAdvantage". On their website, they does, in fact states to read the free report, they will sign you up for "CIC TripleAdvantage", but it's so hidden it's hard to notice.
I bet they must hired ninjas to teach them the art of disguise.

Technically, it's not an unauthorized charge, but it's deceptive advertising.


In the end it says "offer applies with enrollment in TripleAdvantage." Great, it's so loud and clear spoken that people use English as 2nd language can catch that.

I'm not surprised I'm paying for something I never knew I signed up.

Mgccl: Money was taken from my credit card unauthorized.
#lilug
admin_: welcome to america
#mit
brain5ide: heh, Mgccl, I give you an advice - no more online porn
Mgccl: lol, they said it was free1
brain5ide: ok... what kind of idiot you must be to loose your CC info for a website with a word free in it's domain name
Mgccl: it had tv advertising. it's a huge company. FTC had fined it over 15 million dollars. Over 20 million idiots had become one of their prey.
Mgccl: anyway. this is an opportunity to show MIT that I'm capable of taking legal actions

Yeah, this is America.

Guess it's going to be a long battle, I'm going to get my money back and of cause, make the issue so big, they will be facing legal issues, and maybe even publish an commentary on my school newspaper. I don't mind the amount of work in the process.

I need to prepare a sheet of what I'm going to say to w/e the customer's response are, because I can't talk and think at the same time.[Epic Fail for me]

If you have the same problem, this place has the best resource.

  1. 1. I never did or will sign up for any online porn, period.

Save money, extra large or jumbo eggs

Posted October 12th, 2007 by Mgccl
in

Since I have my own credit card, it's my nature to shop for food and act Chinese by being cheap.
Eggs is a must for my diet, so I found 2 packages, one is for 12 extra large eggs, 27 ounces, $1.79. The other is 12 jumbo eggs, 30 ounces, $1.99.
I did some division
27 ounce/$1.79 = 15.0837989 ounce per dollar
30 ounce/$1.99 = 15.0753769 ounce per dollar
Ostrich egg
Clearly, buy extra large eggs is better, I get 0.008422 once more every dollar I spend!
Or is it?

I forgot one thing that could entirely change this simple easy math problem into sophisticated money saving skill.
I don't eat egg shell.
suppose, egg shell have a constant density, which is really possible because it's 95% CaCO3, ds(shell and de for the entire egg) with 2 shell volumes, Vsl(extra large shell) and Vsj(jumbo shell)would large eggs still be the better choice?

27 ounce - ds*Vsl/$1.79 ???? 30 ounce - ds*Vsj/$1.99

so, you can see, what determines everything is the growth of the egg shell's mass VS the growth of the entire eggs mass. The egg's shape is different, but it's possible to see that it can be cut into infinite many infinite small height cylinders, or just consider it as a circle. All I need to do is to prove that for every circle, the increase of the area(the mass = volume * density, and we made volume into area and the ignore the density because the same for all shell) of the entire circle is far greater than the increase of the area of the ring (the shell). This idea always works if the volume of the egg approaches infinity, even though it's not proven to work in this situation, but it's nice to analyze and can come out with some formula that might help with us afterward.

the circle's radius is r, ring's width is w, the equation for the circle's area is:
πr²
for the ring's area is
πr² - π(r-w)²
suppose egg shell's size don't increase (likely, at most, it won't increase more than 1.2 times of it's original width), then the only variable is r. and then you could see, the circle's area grows quadratically, while the ring's area grow linearly.
πr² - π(r-w)² = πr² - πr²+π2rw-πw² = π2rw-πw²
As the egg's volume grow larger, shell's volume proportion to egg's volume gets smaller.

Without knowing each variable's value, the only thing we can use is common sense.
set up this equation
27 - ds*Vsl/1.79 < 30 - ds*Vsj/1.99
now solve it
1.99*(27 - ds*Vsl) < 1.79(30 - ds*Vsj)
53.73 - 1.99ds*Vsl < 53.7 - 1.79ds*Vsj
0.003 - 1.99ds*Vsl < -1.79ds*Vsj
1.11173184ds*Vsl - 0.00167597765 > ds*Vsj

If this holds, then it's better to buy jumbo eggs. is this likely? I don't know, but I believe it's yes. When the volume of the shell increase less than 11% and the egg's volume increase from extra large to jumbo (11%), it is most likely to be true because the constant number is extremely small.

I bought the jumbo eggs. What will you do? btw, price in your area will differ, maybe it's better to buy extra large eggs after all.

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