Ask MetaFilter questions tagged with numbers

RDRR. Get it?

bondcliff — Tue, 01 Dec 2009 07:14:36 -0800

What are some cool math and number facts that would blow the mind of a seven year old? Yesterday at the dinner table my son says "Hey dad, did you know 111,111,111 x 111,111,111 = 12,345,678,987,654,321?"*

He thought this was awesome. I've previously told him the trick about multiplying by 9 (2x9 = 18, 1+8=9, 3x9=27, 2+7=9 and so on up the times table) and a couple of other fun facts.

I'd like to present him with some other neat numerical properties and math facts. He'd need to be able to grasp the concept, so something like the non-palindromic properties of 196 might be a bit beyond him. He's in (the equivalent of) 2nd grade at a Montessori school and math is his favorite subject. He's currently doing 2-digit division and he's pretty much mastered multiplication. I'm not afraid to go a bit beyond what he's learning but I don't want to go too far beyond it.

What can you tell him about other interesting numbers and how to get to those numbers?

Calculator tricks might be fun as well. I'm sure if I teach him the S8008 trick he'll be the King of the Playground. Also tricks that require props such as playing cards, Legos, or anything else are welcome, as long as they demonstrate the type of thing I'm looking for.

I'll take book suggestions as well. Christmas is coming...

*interestingly, the first Google hit for 12345678987654321 is a MeFi thread.

I've told you a million times!

surenoproblem — Sat, 31 Oct 2009 05:57:48 -0800

What are your benchmarks for estimating/comprehending quantities? I'm terrible with magnitudes; if someone tells me that they weigh 85kg, or that they come from a city of 2 million people, this doesn't create a mental picture for me at all; they might as well be speaking another language. After a lifetime of being resigned to this, I've decided I'm going to familiarise myself with a list of benchmark quantities: my height, the height of my tallest friend, population of my city, etc. Help me compile a list of quantities I should be familiar with, and tips for learning to come to grips with quantities! For example, these are some of the quantities I'm going to familiarise myself with:

Population of Australia: 21 million
Population of USA: 304 million
Population of China: 1.33 billion (1,330 million)

My height
Height of tallest friend
Height of short friend

My weight
Weight of buffest dude at my gym

Population of my city
Population of all cities I've lived in

GDP of Australia
GDP of major nations

Distance from my house to the corner shop
Distance from my house to work
Distance to other cities

Any quantities that you find useful, or tips for better visualisation, would be appreciated. Thanks!

Not all random numbers are created equal

monkeystronghold — Sun, 25 Oct 2009 23:30:14 -0800

How do I get a controlled distribution of random numbers to fairly determine a start position. In a sporting event, start position is decided based on the last digit of your registration number. Each week, random numbers are drawn to decide the start order. For example, the random draw order for a single week is 4, 0, 3, 5, 1, 8, 7, 9, 6, 2. So everyone with a number ending in 4 starts first. Everyone with a number ending in 0 starts second. And so on. The next week the draw order is again random.

While this works, the distribution of of numbers can end up being unfair (one particular number can be "lucky" or "unlucky" for many weeks). Statistically, how would one generate a set of "random" start orders so that the value of each registration number was roughly equal over the course of a season (for ease of calculation, let's say 10 weeks).

I don't know anything about math or statistics, so my description of this situation probably uses lots of words incorrectly. I'd google this, but I don't even know how to start.

Basically, is it possible for value of all of the numbers to even out. But in a random order. So, for example, that 0's aren't always going after 4's. And one group doesn't always start in the middle.

The twenty most important numbers

bigmusic — Fri, 23 Oct 2009 14:13:51 -0800

In a talk (at TED) by Brian Greene on string theory he says that there are "there appear to be about 20 numbers that really describe our universe..." He lists a few in his talk, but what are the rest of of those numbers? The pertinent excerpt from the talk:



And that question is this: when we look around the world, as scientists have done for the last hundred years, there appear to be about 20 numbers that really describe our universe. These are numbers like the mass of the particles, like electrons and quarks, the strength of gravity, the strength of the electromagnetic force -- a list of about 20 numbers that have been measured with incredible precision, but nobody has an explanation for why the numbers have the particular values that they do.

I've Got Your Number

kristi — Fri, 16 Oct 2009 11:00:34 -0800

I love numbers! Especially numbers that track things. What services could I offer that involve fairly simple numbers? (Note: no significant statistics background; NOT advanced math.) Lately I've been noticing how much I love tracking things with numbers.

I've been playing with CRONometer (calorie tracking software), and enjoying watching variations in all kinds of measurements (fiber intake! Vitamin A! sodium! Whee!).

I love playing with Quicken and watching the numbers go up and down over time.

I love tracking my website hit stats.

It just all makes me hugely happy.

I currently do website administration and development, with a focus on Drupal, and I'm fortunate enough to have plenty of work at the moment. But I can't help wondering whether there's a service I could provide that would involve this kind of number tracking. I can write clearly and enjoy writing pretty well, so reporting on numbers would be fine. I've even done some week-to-week tracking of AdWords and Google Analytics for a few clients, but I'm not sure how much need there is for that.

Note that I have no real background in statistics, and I am definitely not talking about advanced math here - I hope one day to learn calculus, but that day has not yet come.

So - any suggestions for services I could offer that would involve tracking numbers, and types of customers who might need those services?

Thanks!

Mommy I'm twelveteen now!

Arbac — Sat, 05 Sep 2009 11:43:13 -0800

Why are the teen numbers (13-19) named differently than the rest of the numbers, and what's up with eleven and twelve? I heard a little kid trying to count today and they went ten, eleventeen, twelveteen etc and it got me wondering. Why are the numbers 11-19 named differently than the other numbers?

20-29 is all twenty + one through 9. 30-39 is the same all the way up to 100. So why is it eleven and not tenone?

Wikipedia says that 11 and 12 are derived from german words meaning ten and one left and two left respectively. Ok .. I guess I can understand that, so then what's going on with the teens?

iPhone Swapping: A SIM is a SIM is a SIM?

pzarquon — Thu, 11 Jun 2009 12:23:03 -0800

Two iPhones, a 2G and a 3G, on a family plan. Adding a third, a 3GS. Can I just swap the SIM cards to get the phone numbers onto the devices I want them on, or does AT&T need to get involved? The scenario: I have two iPhones on my current family plan (actually, three, but one isn't going anywhere, so we'll leave that out of the equation). There's a 2G my wife uses, and my 3G. Miraculously, the 3GS comes out just when I started phone shopping for my daughter.

I want to get a 3GS, then "bounce" the SIMs/numbers down the line. In other words, I want the 3GS, my wife would get my current 3G, and my daughter would get the 2G. But my wife and I want to keep our numbers, and give the fresh, new number to my daughter.

In the shuffle, the new phone number SIM that comes with the 3GS would go into a 2G phone, the SIM from the 3G would go into the 3GS, and the the 2G SIM would go into the 3G. While the 3G and 3GS seem to be identical as far as AT&T is concerned, the 2G has a different plan/data with AT&T that's cheaper.

Provided all phones, including the new phone, are properly activated and running with AT&T, can I just put the SIM cards for our respective numbers into the phones I want them to be on?

My feeling is, since we'll still have the same mix of 3GS/3G/2G SIM cards running, it should all work out in the end as long as I pay. AT&T shouldn't care which SIM is in which phone. But, maybe not. Is there any need to involve AT&T in this merry-go-round, or is a SIM a SIM a SIM?

I have me an xls table, I do!

monocultured — Sun, 17 May 2009 16:59:09 -0800

I have an xls file I got from a survey I created on Google docs. Now I want to make it pretty without copy-pasting every bloody cell into an Indesign document… So, using Apples Numbers, I'm trying to change a ≈30×20 table which looks like this:



__________| Q1 | Q2 | Q3 | Q4 |

Timestamp | A1 | A2 | A3 | A4 |

Timestamp | B1 | B2 | B3 | B4 |

Timestamp | C1 | C2 | C3 | C4 |

Into something that looks like this, with each question on a separate page:

Q1:
A1
B1
C1
D1

Q2:
A2
B2
C2
D2

etc.

As well as a version with each timestamp/user on a seperate page:

Q1:
A1

Q2:
A2

Q3:
A3

etc.

Having looked through the Apple tutorials on Numbers as well as browsing the Google docs forums, I'm stumped. Oh ye wizards of tabular data, aid me in this time of need!

I could use Neo Office or any other data-shuffling method (maybe this can be manhandled by egrep in Textwrangler?) as long as I get a result that is printable / pdf-able.

All the answers are of different lenght, (as in B1 might be "yes" while B2 is three paragraphs long) which need to be accounted for. If there's a way to set type, style and so forth at the same time, that would be dandy!

How to develop "number sense"

Busoni — Wed, 15 Apr 2009 10:53:28 -0800

How might a person go about cultivating "number sense"? I mean something different from abstract reasoning. I'm asking how one might develop an intuition for physical concepts such as numbers, lengths, and sizes. Examples might include knowing how many people went to your school, how many yards away is a given building, how large is your apartment, how much does the average American earn, etc. These things could be measured or found out through research, but how might a person develop the ability to give reasonable estimates?

Texan mystery

gleuschk — Tue, 07 Apr 2009 15:31:09 -0800

What city in Texas could be represented by the number 93711195? Or the string GECAAAABA? My sister, who's going to school in Texas, sent me a "scavenger hunt" puzzle asking for my help. The information given was:

1. 0979839153
2. GECAAAABA
3. 123011221963
4. 3332828
5. 35.1931, -101.7492
6. 4326851112
7. 156sw197
8. 93711195
9. DPSQVT DISJTUJ
10. 76134
11. 01110111 01100001 01100011 01101111

She and her friends have worked out almost all of them. Turns out they're all cities or towns in Texas.
1. ISBN of a book set in Marathon
2. ???
3. time and date Kennedy was shot in Dallas
4. patent number for astroturf (Houston [or Leander?])
5. map coordinates in Amarillo
6. phone number in Midland
7. a law case in San Antonio
8. ???
9. some government code associated with Corpus Christi
10. zip code for Ft. Worth
11. binary for "Waco"

She's missing 2 and 8. I think 2 is probably a string of musical notes, but have no idea about 8. Help me look like the omniscient older brother?

24 hours, no more no less? I doubt it.

onshi — Fri, 20 Mar 2009 13:24:36 -0800

Examples of suspiciously round numbers that have, in all probability, been fudged up or down? Extra points for cases where those numbers can be safely discarded in favour of a different, more realistic figure. We just had a refrigerator delivered and we are advised to let it "stand" for 24 hours before plugging it in. The interwebs confirm this as a widely invoked rule of thumb, the rationale being that in a fridge transported horizontally, oil from the compressor seeps into places it doesn't belong such that the fridge mustn't be switched on until the oil has time to settle back into the compressor. If plugged in too soon, the oil tends to block refrigerant lines (negatively affecting cooling performance) and could potentially cause the compressor to fail completely.

I accept this explanation, and am willing to adhere to the 24 hour guideline just to be safe, but I find it incredibly unlikely that a full day (not one hour more or less) is really required for this process; instead, I would suppose the "true" time it takes would be 12-18 hours at most -- potentially far less -- with the remainder added as a safety margin and to account for idiosyncrasies across brands and models. Instead of providing an accurate figure with each model, a nice, round, extra-safe number that's easy to remember is promulgated by the entire industry.

Another example that springs to mind is the maximum recommended dosage information for non-prescription drugs (e.g. not to exceed 1000mg every 4 hours), which must be set well below the "true" toxic dose for safety reasons and to compensate for the low granularity in the "adults" and "children" doses as opposed a more accurate dosage based on body mass (e.g. 300mg per kg per hour). This fudged number -- say, 40% of toxic for a body mass 1 standard deviation below the mean for an adult or child -- would probably be further rounded down to a multiple of the quantity of drug in each tablet. Alternatively, the tablet size would be adjusted to be a factor of the various fudged dosage guideline(s).

So my question to you: which fudged numbers have you come across? Why do you think they are fudged? What factors would need to be taken into account to determine the corresponding "true" number? Anecdotes where you have personally shown the fudged number to be so? Thanks!

What do you call those giant numbers?

setanor — Thu, 12 Mar 2009 11:42:04 -0800

Is there a name for the design trend (I think associated with brutalism) in the 60s and 70s where buildings had enormous, sans-serif italic numbers on the walls indicating address, floor or room number? These were often shades of brown, orange or yellow. I have seen numbers so large that the tops and bottoms are clipped by the floor and ceiling.

C++ and rand()

Ziggy Zaga — Tue, 17 Feb 2009 10:55:51 -0800

C++ and the rand() function. Please explain why this piece of code works the way it does: cout << rand() % 20 << endl; srand(time(0));
cout << rand() % 20 << endl;

This returns a random number between 0 and 20, as promised by the book I'm reading as well as internet tutorials.

If I remove "% 20" from the code and am left with

srand(time(0));
cout << rand() << endl;

This returns a really big number like 1847292034.

Looking at the code, I would think that adding "% 20" should do nothing more than divide a random number like 1847292034 by 20 and return the integer portion (92364601). But instead the compiler parses it in a different way that says not to generate a random number larger than 20.

Am I interpreting this wrong? Why does the compiler interpret this as something other than a mathematical operation? Is this type of thing common in C++?

Thanks!

(I'm using g++ to compile on a Ubuntu system.)

Bike numbers:

furnace.heart — Wed, 21 Jan 2009 17:25:08 -0800

How are motorcycle (or otherwise) race numbers determined? I've searched and searched, but can't find any real reason how race numbers on vehicles are determined. Is it random? Are they placing numbers from certain races?

I just can't seem to find a straightforward answer. Thanks..

Ring Around Your Finger/Rope Around Your Neck, short term/long term

emhutchinson — Sat, 10 Jan 2009 15:06:22 -0800

When you consider marriage, do you have a time frame? Not for the ceremony, mind you, duration of the bond itself. When you were married, did you think forever or hope for ten to twenty? More? And if you are as yet unhitched, do you think towards the future in terms of numbers, or an indefinite?

How do you say 2666 in Spanish?

Bizurke — Mon, 05 Jan 2009 21:53:22 -0800

How do you say 2666 in Spanish? I assume you say "twenty-six sixty-six" in English. What about Spanish?
"Veintiséis sesenta y séis"? "dos mil seisciento sesenta y seis"?

Help me out!

Number Generation Question

Rock Steady — Fri, 12 Dec 2008 10:06:35 -0800

I need to generate the complete series of 5 digit numbers. The catch? Can only use even digits (0,2,4,6,8). I'd like to accomplish this in Excel, if possible.

How can I make Excel tell me when a number is out of sequence?

Beautiful Downtown Burbank — Thu, 20 Nov 2008 18:46:15 -0800

How can I make Excel tell me when a number is out of sequence? I have about 1700 rows of numbers in one column in Excel. I need to know if any of the numbers are out of sequence or equal to each other, and if so, which rows. I am almost a complete Excel novice so please be gentle with me! Thanks in advance.

Welcome to AskMe, Population: why?

Happy Dave — Wed, 01 Oct 2008 03:35:45 -0800

Why do many American and Canadian towns list population numbers as you enter them, e.g. Welcome to Anytown, Population: 3,414 I work sometimes in the US and Canada, and pass such signs all the time, and I'm curious as to the reasoning, culture, laws and requirements that might lead to towns and cities doing this. Obviously I was familiar with it from Westerns as a kid, (generally with a few numbers being scored out after gunfights etc), but I see it everywhere, and I'm genuinely curious: why did towns and cities start doing this, and why do they continue? Is it just custom or is there a law somewhere that requires it?

How to make a theme from all of these numbers?

Kimothy — Mon, 25 Aug 2008 00:41:27 -0800

My nephews have some numerically coincidental birthdays coming up, anyone have any clever ideas that we can use for the occasion? My sister has given me the task of coming up with a clever way of emphasizing the numbers involved with her sons' birthdays.

-One will be 5 on 11-3-08
-The other will be 3 on 11-5-08
-To further the number madness, their party is going to be held on 11-08-08.

My sister wants me to come up with a theme or invitation design - or both. The only specific instruction was that she wanted it make a point of the once in a life-time coincidence of all of the numbers involved.

Bonus info - the boys are very much into Thomas the Tank Engine and Disney's Cars, which they refer to only as "Lightening McQueen."

Mathematical hive mind, Help me be more clever than I am!

Who are you going to call?

woolylambkin — Mon, 14 Jul 2008 01:28:30 -0800

My phone book was recently lost and I'm looking for numbers to populate my new one. I'm getting family and friends but now I'm looking for generally useful phone numbers. Think along the lines of your favorite carry-out place, a cab service, or any number you have that isn't connected to a person you personally know.

Maybe dyscalculia, maybe badly wired neurons

Anonymous — Tue, 22 Apr 2008 17:17:29 -0800

Does anyone have experience with self-treatment as an adult with dyscalculia? I think I may have it, and that I've had it all my life. Whether or not that's so, are there any tricks to "rewiring" yourself? Like many bookish types, I could never handle math. I wanted to like it, since it made so much sense, but the numbers just never would do what the teacher could make them do. The teachers went on about how smart I was, how well I could do if I really wanted to, and how I "just wasn't trying." Eventually, they were right about that.

Now I realize that I have an awful problem with switching numbers around. Tell me to remember that a house is at 9834 Green Street; I will say to myself, "Right -- 9843 Green Street." This must be why the concepts of math seemed so clear to me, but my grades were terrible. Also, I have difficulty visualizing numerals that a person is reciting, while their words instantly appear in my head.

So I check, and check, and do my very best to compensate for myself. You can imagine the kind of trouble this issue would allow a person to get into. Is proofreading all I can do? It's beginning to embarrass me deeply and personally. Have any of you addressed this issue as an adult?

Can a number be funny?

sourwookie — Fri, 07 Mar 2008 19:56:48 -0800

I have a show tomorrow night, I know nothing about sports, and I need to mod a hoodie. Help with funny/edgy names and numbers. So I'm playing with a band tomorrow night and it was decided our dress theme would be any shirt, jersey or jacket with athletic style, including numbers and maybe player names.

So my plan is to pick up a hoodie, and use iron on lettering to put a number and maybe a name on there, but I would like it to be a joke of some sort.

69 is so obvious it's lame, and 42, while a little better, is also too obvious.

Anyone got any name/number combinations to get me going.

What is that building with the giant light up numbers?

activitystory — Tue, 04 Mar 2008 18:36:54 -0800

What is that building on Water Street at John street in downtown NYC (you can see it on street view on googlemaps)? What are those numbers for? Is it a clock or counter or something?

Putting the page numbers exactly where they ought to be?

.kobayashi. — Sun, 24 Feb 2008 12:18:44 -0800

Can you help me figure out Microsoft Word 2007's settings to meet some very precise requirements for page number formatting? For my dissertation, I need to reformat my page numbers so the top of the number is exactly one inch from the top edge of the page, and the right edge of the number is exactly one inch from the right edge of the page. After that, there should be a double space separating the page number from the text.

I've been futzing around for a while with the headers. But I'm clearly overmatched here. Can anyone either give me a step by step through this, or point me to some clearer online instructions than the ones I've seen so far? Thanks so much!

(And yes, I know, I know, Word has lots of problems, but switching programs is a non-starter right now.)