Random Trivia

SixPapaCharlie

SixPapaCharlie

May the force be with you
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Aug 8, 2013
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What random life hacks do you know that may not be common knowledge?

Recently learned this: You know you can tell what direction an exit will be based on where it is placed relative to the sign below it?

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What do you know that others may not?
 
Multiplying any two digit number by 11, the answer will start with the first digit, end with the last digit and the middle digit is the sum of the original two digits.

For instance, 72 x 11 = 792 7(first digit of original #) 9(sum of digits of the original #) 2(last digit of the original #). If the two digits add up to more than 10, carry the one... 57 x 11 = 5(first) 12(sum) 7(last). Carry the 1 from 12 to the left and you end up with 627.

It works for larger numbers as well, but can get more confusing. For instance, 222 x 11 = 2442 (Sort of like above... but keep the first and last digits, add the first and second, then add the second and third).

It rarely comes in handy (How often do you multiply by 11? And the "times 10 plus itself" trick doesn't take that much longer), but I sometimes get strange reactions from people when I can immediately tell them that 74 x 11 is 814.
 
mjburian said:
Multiplying any two digit number by 11, the answer will start with the first digit, end with the last digit and the middle digit is the sum of the original two digits.

For instance, 72 x 11 = 792 7(first digit of original #) 9(sum of digits of the original #) 2(last digit of the original #). If the two digits add up to more than 10, carry the one... 57 x 11 = 5(first) 12(sum) 7(last). Carry the 1 from 12 to the left and you end up with 627.

It works for larger numbers as well, but can get more confusing. For instance, 222 x 11 = 2442 (Sort of like above... but keep the first and last digits, add the first and second, then add the second and third).

It rarely comes in handy (How often do you multiply by 11? And the "times 10 plus itself" trick doesn't take that much longer), but I sometimes get strange reactions from people when I can immediately tell them that 74 x 11 is 814.
Click to expand...

Never knew that.
that's cool.
 
SixPapaCharlie said:
Never knew that.
that's cool.
Click to expand...

:thumbsup:

Wasn't sure how well a (strange) math lesson would come across in text, especially given the time of night. Glad it made sense.

I learned the exit sign trick in my mid-20s, but always wondered why they didn't teach us stuff like that in driver's ed.
 
Detroit to Windsor is the only place where you can drive south from the US to Canada.
 
Parking garages that have an entrance that spirals up and a separate exit that spirals down obviously fill up bottom to top. The last place to fill is the bottom level on the exit side. Just have to go up one level and swing into the exit(might have to disobey a do not enter sign) plenty of prime parking. Or there used to be until you guys learned my secret.
 
The little triangle next to the gas pump icon on your gas gauge points to the side where the filler is. (Handy with strange rental cars.)
 
upstateny said:
The little triangle next to the gas pump icon on your gas gauge points to the side where the filler is. (Handy with strange rental cars.)
Click to expand...

And, I found out the other night that, on our new Toyota, when it's almost empty, the gas gauge needle covers the little gas pump symbol and triangle so you can't see it. Genius designers. :rolleyes2:

:wink2:
 
I liked the 11 multiplier a lot. Good to know.
And since I am an engineer and like simple math, I can throw in something that hopefully all of you know but as I've learned many people actually do not.

When you need to multiply or divide by 5, don't sweat it, just use 2 instead. Yup. 2 and 5 combined form a 10, right? So that's a great complement.
What's 5 times 26? Uhh, who wants to be doing the math .... well, take half and add a 0. So 13 plus a 0 is 130.
Same if you need to divide by 5. Division is even more complicated. So take the double and remove a 0. Divide 130 by 5. Well, 260 minus a 0 is 26. Tada.
Yes, very simple (I assume you see the logic behind this), elegant and useful. Even my wife didn't know that and she has a college degree. But then again, she told me (her words, not mine): "I'm a girl, what do I care?" :D

Thanks for the great random tips, keep 'em coming.
 
BigBadLou said:
I liked the 11 multiplier a lot. Good to know.
And since I am an engineer and like simple math, I can throw in something that hopefully all of you know but as I've learned many people actually do not.

When you need to multiply or divide by 5, don't sweat it, just use 2 instead. Yup. 2 and 5 combined form a 10, right? So that's a great complement.
What's 5 times 26? Uhh, who wants to be doing the math .... well, take half and add a 0. So 13 plus a 0 is 130.
Same if you need to divide by 5. Division is even more complicated. So take the double and remove a 0. Divide 130 by 5. Well, 260 minus a 0 is 26. Tada.
Yes, very simple (I assume you see the logic behind this), elegant and useful. Even my wife didn't know that and she has a college degree. But then again, she told me (her words, not mine): "I'm a girl, what do I care?" :D

Thanks for the great random tips, keep 'em coming.
Click to expand...

The 5 trick seems so obvious in hindsight... but I never knew it! Another great trick! Now I need to only fly planes that burn either 5 or 11 gph. ;)
 
BigBadLou said:
I liked the 11 multiplier a lot. Good to know.
And since I am an engineer and like simple math, I can throw in something that hopefully all of you know but as I've learned many people actually do not.

When you need to multiply or divide by 5, don't sweat it, just use 2 instead. Yup. 2 and 5 combined form a 10, right? So that's a great complement.
What's 5 times 26? Uhh, who wants to be doing the math .... well, take half and add a 0. So 13 plus a 0 is 130.
Same if you need to divide by 5. Division is even more complicated. So take the double and remove a 0. Divide 130 by 5. Well, 260 minus a 0 is 26. Tada.
Yes, very simple (I assume you see the logic behind this), elegant and useful. Even my wife didn't know that and she has a college degree. But then again, she told me (her words, not mine): "I'm a girl, what do I care?" :D

Thanks for the great random tips, keep 'em coming.
Click to expand...

very cool
 
A similar trick works for restaurant tips. Drop the last digit from the total bill and double what's left. That's the tip.

$50 total bill...$5 x 2 = $10 tip. (20%)

Unless your a cheapass (or got less than stellar service).

Then drop the last digit from the bill, take the remaining number and 1/2 of that remaining number, add them together. That's the tip.

$50 total bill... $5 + $2.50 = $7.50 tip (15%)
 
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You all know the jet fuel lbs-to-gal conversion. But In case you don't know it.

Pilot 1: We will need 600 lbs for our next leg.

Pilot 2: (within 3 seconds) 90 gallons it is then.

Pilot 1: Wow that was fast.


1. Take the total Lbs, in this case 600.
2. Drop the last digit (usually a zero, but not always) 60 is what remains.
3. Take half of the remaining value (1/2 of 60) 30
4. Add the halved amount to the previous number (30+60) 90
5. Do this in your head in a matter of seconds and look genius.

This gets you in a real close ballpark. Otherwise devide the lbs by 6.7 to get the gallons.
 
Use a watch to find direction: point the hour hand towards the sun and half way between the hour hand and 12 is south. Convert to standard time first.
 
cgrab said:
Use a watch to find direction: point the hour hand towards the sun and half way between the hour hand and 12 is south. Convert to standard time first.
Click to expand...
This is great advice and all but what if I'm headed north and not south?


And What if you live in Arizona?
 
cgrab said:
Use a watch to find direction: point the hour hand towards the sun and half way between the hour hand and 12 is south. Convert to standard time first.
Click to expand...

I need to see a diagram
 
Sorry if this is a widely known fact, but if you keep making funny faces it'll get stuck that way.*

*Hopefully citing my Mom as the source of this fact is sufficient.
 
Temperature C to F
Cx2-10% + 32=F
20x2=40
40-4=36
36+32=68

Steel weighs 0.2836 lb/in^3
Aluminum weight 0.09 lb/in^3

Engine HP/20 ~= hourly fuel burn in gph

Cross country flight time is always equal to bladder capacity + 1/2 hour.
Pee bottle is always equal to bladder capacity - 4 oz.
 
Norman said:
Quicker than making pi. :D
Click to expand...

As for Pi, back in the days before scientific calculators 355/113 was a much better approximation of Pi than the widely taught 22/7.

22/7 is good to two decimal places

355/113 is good to six decimal places

Piece of cake!
 
PRO TIP:

If you hold your Landing Calculator vertical, you can actually use it to compute your optimal decent rate in to the pattern. If you hold it vertical and upside down, you can use it to compute your optimal climb rate.
 
If a table is very wobbly don't put a match book or coasters under the "shorter" leg. Turn the table 90 degrees at a time until it doesn't wobble any more. It's simple mathematics.
 
Great stuff!!

The Celsius to Fahrenheit and vice versa one I learned was:

To get Celsius:

F - 32 then divide by 2

So 72 deg F = (72-32)/2 or 40/2 = 20 deg C

The reverse also works:

20 deg C * 2 +32 or 40 +32 = 72 deg F

This gets you in the ballpark and is more accurate for more moderate temperatures*. 72° deg F is actually 22.2 deg C and 20 deg C is actually 68 deg F, but it gets you close enough to understand about what that temp would feel like.

* for instance 98 deg F (98-32)/2 = 66/2 = 33 deg C

98 deg F is actually 36.66 deg C

I have no idea how cold or hot a Celsius temperature is, and a person from Eastern Europe living here didn't know what in the world Fahrenheit temperatures meant. She shared that quick method with me.
 
David7700 said:
Great stuff!!

The Celsius to Fahrenheit and vice versa one I learned was:

To get Celsius:

F - 32 then divide by 2

So 72 deg F = (72-32)/2 or 40/2 = 20 deg C

The reverse also works:

20 deg C * 2 +32 or 40 +32 = 72 deg F

This gets you in the ballpark and is more accurate for more moderate temperatures*. 72° deg F is actually 22.2 deg C and 20 deg C is actually 68 deg F, but it gets you close enough to understand about what that temp would feel like.

* for instance 98 deg F (98-32)/2 = 66/2 = 33 deg C

98 deg F is actually 36.66 deg C

I have no idea how cold or hot a Celsius temperature is, and a person from Eastern Europe living here didn't know what in the world Fahrenheit temperatures meant. She shared that quick method with me.
Click to expand...

And I forget which but it works out that one C and F are equal.
I think it is -46 or maybe -42


Edit: -40C = -40F
 
A simpler ballpark estimate is 2 * Celsius + 30 = Fahrenheit
 
NJP_MAN said:
If a table is very wobbly don't put a match book or coasters under the "shorter" leg. Turn the table 90 degrees at a time until it doesn't wobble any more. It's simple mathematics.
Click to expand...

What if one leg is shorter? :popcorn:;)
 
I have found that there are three ways to try to plug in a mini USB cable connector, and only one way will work.
 
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