Calculating when future percentages will occur.

Yesterday we explored percentage of one’s life, and today we will expand on those figures and attempt to figure out when a particular percentage will occur in the future.

We determined that my girlfriend and I have been together for 10.109% of my life. (Today that number changed to 10.119%)

Today’s question: On what date will we hit the 20% mark? 50%?

To start off, we need to figure out our starting point. How many days into my life did the zero mark occur – or better stated, how many days into my life did I meet my girlfriend?

To figure this out, we need to determine how many days are between Sept 23,1980 (my birthday) and March 12, 2005 (the day her and I started dating). In this case it equals 8,932 days.

We need to adjust our standard equation for finding percentages next:

Part P

——— = ——— We now know our percentage, we just need to know the number of days to make this percentage.

Whole 100

D 20(percent)

———— = ——————-

8932 + D 100(percent)

Basically, we are now saying “How many days into the relationship (D) have to pass before that number equals 20% of my entire life (8932 + D)?”

We need to cross multiply:

100D = 20(8932 + D)

Simplify:

100D = 178640 + 20D

Subtract 20D from both sides.

80D = 178640

Divide both sides by 80.

D = 2233

That means 2233 days from the start of my relationship (or 2233+8932 days since I was born), I will be at the 20% mark.

Using this page: http://www.timeanddate.com/date/dateadd.html, we find that 20% will occur on April 23, 2011.

For 50%, we can take a few shortcuts if we think about the question we are asking.

When will I have spent half of my life in this relationship? Restated, that asks when will the days before I met her equal the days after I met her?

So, 8932 days + 8932 days = Number of days at which point 50% occurs (from my birthday.)

8932 + 8932 = 17864 days from my birthday, or Tuesday, August 21, 2029.

See how it works for you!

CD

Exploring percentages of one’s life.

For my first post, I would like to explore percentages, specifically the percentage of a specific period of time in relation to the total amount of time the person is alive. Let me give you an example:

I have been with my girlfriend since March 12, 2005. As of today (12/11/07), that equals 1005 days.

I was born on September 23rd, 1980. As of today, that equals 9941 days.

We need to come up with an equation that allows us to calculate the percentage of days that I have been with my girlfriend out of the total number of days that I have been alive.

The standard equation for finding a percentage is simple:

Part P

——— = ——— (with P equaling the percentage we are looking for.)

Whole 100

Part would equal 1005 days, because it represents a part of my life of which I am looking for the percentage.

Whole would equal 9941 days, because it represents my whole life, so far.

It would look like this:

1005 P

——— = ———

9941 100

If we solve by cross multiplying,

1005 * 100 = 9941 * P

Then simplify,

100500 = 9941 * P

Divide both sides by 9941 to get the variable by itself on one side of the equation:

10.109 = P

I have been with her for exactly 10.109% of my life, (and let me say that is has been an amazing 10.109%!)

You can use this formula to find this type of percentage for just about anything: Percentage of days spent in school, percentage of days spent in your curent job, percentage of days spent in your current house…the possibilities are endless.

For some help figuring out the number of days (in your life, in your relationship, etc) check out this page:

http://www.timeanddate.com/date/duration.html

Tomorrow we will attempt to find the exact day (in the future) I will hit the 20% and 50% mark.

CD