conundrum!

[anotheranon]

Can someone please tell me why/how this works? Some of you may have already been spammed by this, but I include, in case you haven't:

Subject: age by chocolate...fun one

It takes less than a minute.......
Work this out as you read.
Be sure you don't read the bottom
until you've worked it out! This is
not one of those waste of time things, it's fun.
Go ahead

1. First of all, pick the number of times a week that you would like to
have chocolate.
(more than once but less than 10)

2. Multiply this number by 2 (Just to be bold)

3. Add 5. (for Sunday)

4. Multiply it by 50.
I'll wait while you get the calculator................

5. If you have already had your birthday this year add 1754....If you
haven't, add 1753 ........

6. Now subtract the four digit year
that you were born.

You should have a three digit number .....

The first digit of this was your original number (i.e., how many times
you want to have chocolate each week).

The next two numbers are ..

YOUR AGE! (Oh YES, it is!!!!!)

THIS IS THE ONLY YEAR (2004) IT WILL EVER WORK, SO SPREAD IT AROUND
WHILE IT LASTS.

Calculated, and by doG, it did work, but WHY?

Comments

[nminusone.livejournal.com]

I feel like a goddamn algebra teacher, but what the hell.

For tricks like this you just take all the numbers you're asked to provide and replace them with x, y, etc, depending on how many values you're asked to supply. Then you solve the problem generically, using those variables rather than the actual values. This usually makes things clear.

Let

x = # of times you want to have chocolate per week
y = the year you were born


The various steps ask you to calculate as follows:

step 1:

x

step 2:

2x

step 3:

2x + 5

step 4:

50 * (2x + 5)
which simplifies to
100x + 250

For the sake of ease we will suppose you've already had your b'day this year. More on this later.

step 5:

1754 + 100x + 250
which simplifies to
2004 + 100x

step 6:

2004 + 100x - y
which rearranges to
(2004 - y) + 100x

If you've already had your b'day this year, 2004 minus your birth year (y) gives your age. (If not, you need to use 2003 - y, since birthday wise you've only reached 2003. So the (2004 - y) term represents your age.

The 100x term just takes the first number you put in, the # of times per week you want chocolate, and moves it into the hundreds column. Note how they limit your choices to a number between 2 and 9, inclusive.

The trick breaks down if you're 100 yrs old or more, since your age will overflow into the hundreds column.

[anotheranon.livejournal.com]

Once you break it down into step-by-step with x and y, it does make more sense. I can just grasp it with the tip of my mind.

Having said this, it seems like someone took an awful lot of trouble to do a little mathematical trick - or at least it seems like a lot of trouble to me, math-semi-illiterate that I am :/ To others (like you, and perhaps, my dad), this may seem like a fun way to spend an afternoon :)