## Search found 139 matches

Fri Apr 07, 2017 9:02 pm UTC
Topic: 1821: "Incinerator"
Replies: 25
Views: 7186

### Re: 1821: "Incinerator"

How would you dispose of the word's biggest trash can?
Fri Sep 14, 2012 1:44 am UTC
Forum: What If?
Topic: What-If 0011: "Droppings"
Replies: 68
Views: 32069

### Re: What-If 0011: Droppings

Once I was lying on my back on the lawn and a hummingbird peed/pood in my eye. It was flying by 15 or 20 feet above me and I clearly saw, and then felt, a small single drop of ick fall from it to me.
Thu Jun 07, 2012 6:45 pm UTC
Forum: Mathematics
Topic: Stumped on this problem: probably calculus
Replies: 7
Views: 1705

### Re: Stumped on this problem: probably calculus

Once I had the solution from Qaanol it led me to a more simple solution that does not require calculus: in this problem the stirring does not matter at all. The average age of the exiting water must be [size of chamber] / [flow rate], giving 1 for the original problem.
Thu Jun 07, 2012 4:26 am UTC
Forum: Mathematics
Topic: Stumped on this problem: probably calculus
Replies: 7
Views: 1705

### Re: Stumped on this problem: probably calculus

Great explanation, thank you.
Thu Jun 07, 2012 2:46 am UTC
Forum: Mathematics
Topic: Stumped on this problem: probably calculus
Replies: 7
Views: 1705

### Re: Stumped on this problem: probably calculus

Qaanol wrote:Your scenario yields a differential representation as A′=1-bA. Do you see why?

Nope.
I understand the equation and can solve from here, but I do not see how this equation comes from the problem.
Thu Jun 07, 2012 1:02 am UTC
Forum: Mathematics
Topic: Stumped on this problem: probably calculus
Replies: 7
Views: 1705

### Stumped on this problem: probably calculus

I came up with this idea while attempting to devise devious bonus problems for students, but have not yet been able to solve. A 1 liter tank has a an intake pipe and an output pipe. The tank is initially full. Beginning at t = 0, water flows in to the tank through the intake at 1 liter per hour and ...
Wed May 16, 2012 4:18 am UTC
Topic: 1056: "Felidae"
Replies: 170
Views: 46528

### Re: 1056: Felidae

OS Maru.
Wed Nov 09, 2011 6:43 pm UTC
Forum: Mathematics
Topic: Conditional Probability Question
Replies: 16
Views: 4209

### Re: Conditional Probability Question

First, it is not ok that this irresponsible pet owner has p=.4 for not feeding their dog. Second, Also, to make it more intuitive / easier to visualize, you may want to imagine that instead of 1 dog, you have a large number of (say 1000) identical dogs. This is a very, very fun thing to imagine. Don...
Thu Oct 13, 2011 2:52 am UTC
Forum: Mathematics
Replies: 46
Views: 14940

### Re: Your favorite "tricky" integrals?

Sat Oct 01, 2011 11:00 pm UTC
Forum: Mathematics
Topic: vote counting probability puzzle
Replies: 2
Views: 779

### Re: vote counting probability puzzle

elegant
Sat Oct 01, 2011 8:58 pm UTC
Forum: Mathematics
Topic: vote counting probability puzzle
Replies: 2
Views: 779

### vote counting probability puzzle

A co-worker brought this one in, from an older collection in a book of puzzles. Alice and Bob (and no other candidates) ran for mayor. Alice won the election with 300 votes, to Bob's 200. The votes were counted one at a time, in random order. As each vote was counted the totals so far were announced...
Wed Aug 10, 2011 5:45 pm UTC
Replies: 893
Views: 320792

I'll share a system I read about to create multiple easy to remember and hard to bruteforce passwords for different sites 1) make an anagram from a memorable phrase, with number/symbol substitution and/or capitalization (6-8 characters) Bugs Bunny gives me funny feelings = bbgmff = 88gmFF 2) for eac...
Wed Mar 30, 2011 4:02 am UTC
Topic: 0879: "Lamp"
Replies: 151
Views: 37182

### Re: 0879: "Lamp"

your wish is my come, man.
Thu Jan 06, 2011 7:36 pm UTC
Forum: Mathematics
Topic: AP Calc: Are there practice tests with 2011 rule changes?
Replies: 1
Views: 530

### Re: AP Calc: Are there practice tests with 2011 rule changes

I'll answer my own question: I got the info from another forum but I'll share it here:
http://apcentral.collegeboard.com/apc/p ... 12187.html
This page has updates to old (for sale) practice exams with scoring keys under the new system.
Thu Jan 06, 2011 4:44 pm UTC
Forum: Mathematics
Topic: AP Calc: Are there practice tests with 2011 rule changes?
Replies: 1
Views: 530

### AP Calc: Are there practice tests with 2011 rule changes?

The AP Calculus exam will have 2 rule changes for the 2011 test dates: There is no longer a penalty for incorrect multiple choice answers (instead the thresholds for earning a 2/3/4/5 will be higher) There will be 4 free response questions with calculator use allowed and 2 without (used to be 3 of e...
Fri Dec 31, 2010 6:12 am UTC
Topic: 0841: "Audiophiles"
Replies: 266
Views: 52646

### Re: 0841: Audiophiles

Fri Dec 10, 2010 6:07 am UTC
Forum: General
Topic: Logical fallacies/douchebaggery in commercials.
Replies: 4973
Views: 760545

### Re: Logical fallacies/douchebaggery in commercials.

I am confused by commercials for televisions that show you how good the picture on the television looks.

Let's get that tv, the picture looks way better than ours does! o wait...
Thu Oct 07, 2010 8:43 pm UTC
Forum: Mathematics
Topic: Order of operations for trig, logarithms
Replies: 11
Views: 5376

### Re: Order of operations for trig, logarithms

mike-l wrote:No, it shows that the multiplication is applied first.

Shamed. I'll refrain from destroying the evidence of my blunder by edit, it would cause subsequent posts to no longer make sense.

pemdTLas
Thu Oct 07, 2010 8:26 pm UTC
Forum: Mathematics
Topic: Order of operations for trig, logarithms
Replies: 11
Views: 5376

### Order of operations for trig, logarithms

grade schoolers learn PEMDAS as an acronym for order of operations (parentheses, exponents, multiply and divide, add and subtract), but this doesn't tell what order to read expressions involving trig or logarithm In general, from my experience sin x^2 is read as sin (x^2) , not (sinx)...
Thu Sep 23, 2010 6:21 pm UTC
Forum: Mathematics
Topic: r = theta, convert to rectangular coordinates?
Replies: 11
Views: 11488

### Re: r = theta, convert to rectangular coordinates?

Well, look at the graph. For any x there are an infinite number of y that satisfy it. You're not going to turn it into a function without specifying half of a single arc, and I can't imagine that would be very valuable. That's exactly what we're looking for, actually. Can a given section of the spi...
Thu Sep 23, 2010 5:58 pm UTC
Forum: Mathematics
Topic: r = theta, convert to rectangular coordinates?
Replies: 11
Views: 11488

### Re: r = theta, convert to rectangular coordinates?

You'll end up with something genuinely hideous, and that's okay. I'm fine with hideous, but I cannot get to a function of y strictly in terms of x. There's always an r or theta left that I cannot substitute out. or directly, root(x^2 + y^2) = arcsin (y/r) for positive x so root(x^2 + y^2) = arcsin ...
Thu Sep 23, 2010 4:56 pm UTC
Forum: Mathematics
Topic: r = theta, convert to rectangular coordinates?
Replies: 11
Views: 11488

### r = theta, convert to rectangular coordinates?

Express r = theta in rectangular coordinates.

It's not my homework, but it's a problem in the 'precalculus-review' section of a mainstream calculus textbook (Larson, section 10.4, #39).

My normal approach is useless here.
Wed Aug 25, 2010 4:01 am UTC
Topic: 0784: "Falling Asleep"
Replies: 96
Views: 29075

### Re: Falling Asleep discussion (784)

zzz
Fri Apr 16, 2010 4:07 am UTC
Replies: 63
Views: 15865

There are, right now, monkeys controlling robotic arms via neural implants.

Pics or it didn't happen.
Tue Nov 17, 2009 9:29 pm UTC
Topic: 0663: "Sagan-Man"
Replies: 107
Views: 24063

### Re: "Sagan-Man" Discussion

The Pale Blue Dot quote reminded me of this photo taken by Cassini.

We are
Spoiler:
just beyond the brightest ring, at about 10 o'clock.
Tue Oct 27, 2009 9:51 pm UTC
Forum: Science
Topic: reinventing the wheel (or watch)
Replies: 44
Views: 5488

### Re: reinventing the wheel (or watch)

gmalivuk wrote:
oblivimous wrote:Iron, Silicon, Uranium, etc. are all as easy to acquire on this island as they are at their most accessible locations elsewhere on earth.

Now or when those things first began to be used?

When those things first began to be used.
Tue Oct 27, 2009 5:34 pm UTC
Forum: Science
Topic: reinventing the wheel (or watch)
Replies: 44
Views: 5488

### reinventing the wheel (or watch)

A team of ten people are chosen from among the best minds of modern science and engineering to work on a unique project, with a preference for people who also have relevant practical skills in areas such as mining, metallurgy, blacksmithing, etc. These people are placed on a deserted island with no ...
Fri Oct 16, 2009 7:26 pm UTC
Forum: School
Topic: High School Pranks
Replies: 684
Views: 89924

### Re: High School Pranks

Amishdemon wrote:My brother wanted to fill water balloons with paint and the put them in the hallway and see what happens.

JELL-O. Fill them with Jell-O

1) Make Jello
2) In liquid form, pour into balloons. From a 2-liter bottle.
3) Balloons in fridge.
Fri Oct 09, 2009 5:36 pm UTC
Topic: 0647: "Scary"
Replies: 271
Views: 58956

### Re: "Scary" Discussion

America is less than three lifetimes old. If I was born in 1825-1845 and lived to 100, then in my childhood I met elders who remembered the revolution and in my old age I met children who still live. Regarding Mother Jones, Utah Phillis said: "It is hard for the mind to encompass the life that ...
Sun Jul 12, 2009 4:26 pm UTC
Forum: Mathematics
Replies: 53
Views: 9685

For many students, integration is an exciting topic because, especially at first, every problem is a puzzle. After years of doing mathematics where textbook-drill-problems can be solved by rote, suddenly problems require varying degrees of cleverness. Let's collect the best here. Problems should be ...
Sun Jul 12, 2009 4:04 pm UTC
Forum: Mathematics
Topic: Boundary Optimization
Replies: 16
Views: 1355

### Re: Boundary Optimization

If you count overlaps, then my first thought would be to run a circle N m in circumference, so if you lose all your energy, you've maximised the area. Then I'd repeat this with what energy is left, and repeat this with what energy is left.... and so on. If by "overlaps" you mean winning m...
Sat Jul 11, 2009 11:40 pm UTC
Forum: Mathematics
Topic: Boundary Optimization
Replies: 16
Views: 1355

### Boundary Optimization

There’s an old story about a man who is told that he will be given ownership of whatever section of land he can run the perimeter of in one day. He gets greedy and pushes his physical limits, but just makes it back to the starting point at the deadline. Then he drops dead from exhaustion. There’s pr...
Wed Jun 24, 2009 12:34 am UTC
Topic: 0600: "Android Boyfriend"
Replies: 136
Views: 43825

### Re: "Android Boyfriend" Discussion

It's not ok that the sound effects remind me of this
Tue Jun 16, 2009 4:36 pm UTC
Forum: Music
Topic: Most ridiculous music myth you ever heard
Replies: 46
Views: 5005

### Re: Most ridiculous music myth you ever heard

George Clinton has a BA in mathematics.
Tue Jun 16, 2009 4:36 pm UTC
Forum: Music
Topic: Headphones that can take wear-and-tear.
Replies: 18
Views: 2759

### Re: Headphones that can take wear-and-tear.

Senn's are good, but you can't beat the Grado 60's for sound quality or durability. They're \$80 new, not too hard to find used. Only negative, they use a 1/4" jack, so you'll need an adapter, and they have a cord about twice as long as it should be (which is a bonus if you ever want to plug int...
Fri Jun 05, 2009 3:17 pm UTC
Forum: Mathematics
Topic: Why does the letter "b" represent the y-intercept?
Replies: 23
Views: 5864

### Re: Why does the letter "b" represent the y-intercept?

Sir_Elderberry wrote:Considering how they teach quadratics, y = ax + b makes much more sense.

Considering how they teach quadratics, y = bx + c would make the most sense, and, afaik, nobody uses that form.
Sun Apr 05, 2009 6:38 am UTC
Forum: General
Topic: Uh-oh. It's a Youtube party and you're up next. What do you show 'em?
Replies: 2151
Views: 748247

### The worst thing on youtube

You'll never watch Karate Kid II the same way again.
Got worse?

Edit: edited.
Wed Mar 04, 2009 5:34 am UTC
Topic: 0551: "Etch-a-Sketch"
Replies: 124
Views: 26123

### Re: "Etch-a-Sketch" Discussion

There's a guy in the niegborhood who is a genius with the sketch. Here's some of his work. His site is http://www.michaelmcnevin.com/ http://www.michaelmcnevin.com/images/etchasketchofbagger.jpg http://images.tribe.net/tribe/upload/photo/727/3ba/7273ba02-b894-4da1-8fe7-ce1e10a41d11.large-profile.jpg
Fri Jan 30, 2009 10:52 pm UTC
Topic: 0537: "Ducklings"
Replies: 150
Views: 46800

### Re: "Ducklings" Discussion

dennisw wrote:
There are six flavors of quacks: Up, Down, Top, Bottom, Strange, Charm

I thought all quacks were down.
Fri Jan 30, 2009 9:46 pm UTC