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11 Math Tricks That Will Make Your Life So Much Easier (from investing to remembering time)
Business Insider ^ | 03/11/2013 | Walter Hickey

Posted on 03/11/2013 7:48:26 AM PDT by SeekAndFind

You're on the trading floor, trying to price out if a 15-year bond issued by General Electric will generate the returns needed to placate your investors.

Well, if all you need to do is double the investment in five-years, you're in luck.

That's probably not the case, and maybe GE isn't issuing 15-year debt. But we compiled a list of eleven math tricks that might just come in handy at various times in life.

If you have a math trick you'd like us to add, leave it in the comments.

1) The Rule of 72

Need an easy way to determine how long it will take to double your returns? Simply divide the number 72 by your projected growth rate.

So, if your returns are increasing by 10 percent per year, it will take 7.2 years for them to double in size.

2) The Rule of 115

If you're more inclined to triple your returns, because you're not as risk averse (or perhaps your time horizon is just a tad bit farther out), simply take the number 115 and divide it by your growth rate. This will give you the amount of time it will take to triple your returns.

So, if your returns are increasing by 10 percent per year, it will take 11.5 years for them to triple in size.

3) The Rule of 70

Magyar Nemzeti Múzeum Történeti Fényképtára, Budapest The rule of 70 dictates how long it will take for inflation to halve the value of a dollar. Simply divide 70 by your expected rate of inflation.

KEYWORDS: math; mathtricks

1 posted on 03/11/2013 7:48:26 AM PDT by SeekAndFind

To: SeekAndFind

FOR THOSE OF YO WHO ARE LUCKY TO HAVE A FULL TIME POSITION IN THE OBAMA ECONOMY:

Converting your salary to an hourly figure

You’re a salaried employee and trying to figure out how much that wage earns you an hour, maybe for that part-time job you’re considering taking on. Take your salary, drop the last three zeros and then divide by the number two.

So if you earn \$40,000, you’re left with \$20 an hour.

Numbers work best if you’re only working a 40 hour week.

2 posted on 03/11/2013 7:51:00 AM PDT by SeekAndFind

To: SeekAndFind

TO THOSE WHO ARE COUNTING THE YER BEFORE RETIREMENT AND ARE WONDERING HOW TO INVEST IN AN IRA OR 401K:

Asset Allocation by Age

This one really isn’t a math trick, so much as it is a rule of thumb...

Don’t have a financial planner to walk you through asset allocation? A simple way to find out is to subtract your age from the number 120, the number remaining is the percentage of your portfolio that should be in stocks.

For instance, if you’re 50, you should be keeping 70% of your holdings in stocks with the remaining 30 percent in fixed income products.

3 posted on 03/11/2013 7:52:16 AM PDT by SeekAndFind

To: SeekAndFind
1) The Rule of 72
3) The Rule of 70

These are basically the same whether you are figuring out how long it takes to double your money or for your money to halve by itself. The actual number is log(2)/log(1+R/100).

The rule of 72 is more accurate for 5% and above.

4 posted on 03/11/2013 8:03:41 AM PDT by KarlInOhio (Choose one: the yellow and black flag of the Tea Party or the white flag of the Republican Party.)

To: SeekAndFind

thank you! I am going to keep these handy!

5 posted on 03/11/2013 8:05:01 AM PDT by austinaero

To: SeekAndFind

1) The Rule of 72

Need an easy way to determine how long it will take to double your returns? Simply divide the number 72 by your projected growth rate.

Learned that one as a kid on an old rerun of The Lucy Show where she was trying to scam a double-your-money-back offer on baked beans.

6 posted on 03/11/2013 9:18:32 AM PDT by Buckeye McFrog

To: SeekAndFind

The rule of 70 dictates how long it will take for inflation to halve the value of a dollar.

Simply divide 70 by your expected rate of inflation
mulitiplied by years Obama is in office.

7 posted on 03/11/2013 9:21:19 AM PDT by TurboZamboni (Looting the future to bribe the present)

To: SeekAndFind

Later for numbers

8 posted on 03/11/2013 9:23:31 AM PDT by I_be_tc

To: SeekAndFind

math tricks

9 posted on 03/11/2013 9:36:37 AM PDT by quintr

To: TurboZamboni

RE: Simply divide 70 by your expected rate of inflation
mulitiplied by years Obama is in office.

The question is this -— Should we believe the official CPI? If you can’t determine the real inflation rate, then yo can’t compute accurately. Garbage in, garbage out.

10 posted on 03/11/2013 9:51:33 AM PDT by SeekAndFind

To: SeekAndFind
Here's an interesting mathematical oddity that I learned about a few months ago...

Take any number.

If the number is even, divide by 2

if the number is odd, multiply by 3, then add 1

Take the result and process it in the same way.

You will eventually end up at 1

Here's the series you'd have if you start with the number 13:

13 40 20 10 5 16 8 4 2 1

Starting with 12:   12 6 3 10 5 16 8 4 2 1

This is called the Collatz Conjecture. The article in Wikipedia is really interesting.

Check out the number of steps for startnig numbers of 26, 27, and 28.

26 13 40 20 10 5 16 8 4 2 1

27 82 41 124 62 31 94 47 142 71 214 107 322 161 484 242 121 364 182 91 274 137 412 206 103 310 155 466 233 700 350 175 526 263 790 395 1186 593 1780 890 445 1336 668 334 167 502 251 754 377 1132 566 283 850 425 1276 638 319 958 479 1438 719 2158 1079 3238 1619 4858 2429 7288 3644 1822 911 2734 1367 4102 2051 6154 3077 9232 4616 2308 1154 577 1732 866 433 1300 650 325 976 488 244 122 61 184 92 46 23 70 35 106 53 160 80 40 20 10 5 16 8 4 2 1

28 14 7 22 11 34 17 52 26 13 40 20 10 5 16 8 4 2 1

When I first started playing with this, I started looking at some of the interesting patterns and properties associated with it. I wrote a few shell scripts to look at different aspects of it. One interesting point is that when you are calculating the sequence for a particular number, once you hit a number you've already done, since you already know the 'path' taken from that number, you can stop and just refer to it rather than confinue along. This really sped things up once I started incorporating that into my shell scripts.

11 posted on 03/11/2013 10:16:06 AM PDT by zeugma (Those of us who work for a living are outnumbered by those who vote for a living.)

To: SeekAndFind

Just divide your annual salary by 2080 (the “standard” hours in a work year, which is 40 hrs a week times 52 weeks, including vacation and sick time).

I’ve done that since I was 15.

12 posted on 03/11/2013 12:49:43 PM PDT by ro_dreaming (G.K. Chesterton, Â“Christianity has not been tried and found wanting. ItÂ’s been found hard and lef)

To: SeekAndFind

1 + 1 = 0 after taxes..........

13 posted on 03/11/2013 12:57:18 PM PDT by Osage Orange (Life is a bitch. If it was easy, we would call it a slut)

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