Sunday
February 7, 2016

# Posts by jim

Total # Posts: 1,571

Math
The reason you didn't think of that is just that you haven't had enough practice yet. :-) Keep plugging at it, and you'll be doing these things without even having to think about them!
October 17, 2009

Math
Good question! Really good question, since you're thinking of the more general case. You can't use the same trick there; I'm afraid you'll have to calculate. The standard way, that will always work, is to find a common denominator of the two fractions, so that ...
October 17, 2009

Math
October 17, 2009

Math
Right! If it's bigger than one, the number on top is larger. Now, is 19/6 greater or less than one? Is 4/27 greater or less than one? So without calculating anything, you can show that the two fractions cannot be equal.
October 17, 2009

Math
I like this question! It's simple, but should make you think, and there are many ways to approach it. I'd hate to deprive you of the thinking experience, but here are some questions for you. What does it mean for a statement about numbers being equal to be "true&...
October 17, 2009

Science
Search for "population ecology" and "population biology". You might find what you're looking for there. I think "population ecologist" may be the term you're looking for.
October 17, 2009

science
October 17, 2009

science
1800g = 1.8kg How many 1.8 kg are in 80 kg?
October 17, 2009

math (algebra)
Take the next one then. Step by step. 9x = 5y + 3 Parallel, but going through (-2, 4). x is -2. y is 4. It must be 9x = 5y + something 9*-2 = 5*4 + something. What is the something?
October 16, 2009

math (algebra)
That's OK. First you solve it. Then you put it into the form you need. Point slope form just means moving y to the left hand side, and everything else to the right. Consider: x + 5y = 47 Subtract x from both sides: 5y = 47 -x Divide by 5 y = 47/5 - x/5
October 16, 2009

math (algebra) -oops
I typoed, and it might confuse you. Sorry. 5*8 is 40, or course, not 47. x + 5y = something 7 + 5 * 8 = something 7 + 40 = something = 47 So a line parallel to x+5y=2, containing (7,8) is x+5y=47.
October 16, 2009

math (algebra)
The key point to know is that: if the new line is parallel, then the coefficients of x and y will be the same (The coefficients are the numbers that x and y are multiplied by). So, taking the first one, any line parallel to x+5y=2 will be of the form x + 5y = some_number x + ...
October 16, 2009

algrbra 2
Divide the difference in the y coordinates by the difference in the x coordinates to get the slope.
October 16, 2009

Algrbra 2
This is quite straightforwatrd. x is 15, so 15 - 5*y = -25 so what is y?
October 16, 2009

math
I think maybe what's being asked is to get an equation with B on the left-hand side. A=(1/2)BH multiply both sides by 2 2A=BH divide both sides by H 2A/H = B so B = 2A/H
October 16, 2009

calculus - identities
sec(y)=1/cos(y) tan(y) = sin(y)/cos(y) Low consider left and right hand sides: LHS = 1/cos(y) - cos^2(y)/cos(y) RHS = sin^2(y)/cos(y) Now you've got everything over a common denominator, look at the top of each side, and you should see your way through.
October 16, 2009

Aristotle had the (very wrong) idea that things could move only as long as something was pushing them. This no doubt seemed reasonable in Earth conditions, before quantitative science, when just about everything that moves is pulling against gravity or friction. In a vacuum, ...
October 16, 2009

intro to software development
If it's any comfort, I don't quite know what they're asking either, "Processes or capabilities" could mean almost anything. I have a suspicion I'm telling you much more than you need to know. If I were writing one, I'd identify: data capture (...
October 16, 2009

calculus
Differentiate to find the max height. Velocity is 64 - 32t. Max is at s'(t) = 0, when velocity is zero s'(t)= 64 - 32t = 0 so it peaks at t=2. From that you can get the height. You now need to find s(t) = 0, so solve 64+64t–16t2 = 0 That will give you the time, ...
October 16, 2009

calculus
The slope of the tangent at that point will be the same as the slope of the parabola, by definition. How do you get the slope of the parabola at that point? Differentiate it. What is the differential of 4x^2–6x+6? Now plug in x=5 to your answer, and the arithmetic gives ...
October 16, 2009

Math- Graphing Calculator Use
I'm sorry, but I'm not sure anybody will be able to help with that information. Different calculators do stats, especially, in different ways. If you specified the exact model you're using, maybe somebody reading this would have the same one, and know how it works...
October 16, 2009

Calculus
Well, the derivative of sin is cos, and the derivative of cotan is cosec^2, both of which should be in your standard list of derivatibes. Knowing that, you can just write down the answer.
October 16, 2009

math
4 seconds PLUS how many seconds in a minute? multiply that by 36 PLUS how many seconds in a minute? multiply that by how many minutes in an hour and multiply again by 23 That is, 23 * 60 * 60 + 36 * 60 + 4 For a check on your answer, it'll be a five-digit number like 8???4
October 16, 2009

Calculus
I can't find an integer n for which this is true. Consider f'(x) = 1/(2sqrt(x+6)) =1/2sqrt(52) at point x=46 You can take a factor of 4 out of that, =1/4sqrt(13) but you're still left with the irrational sqrt(13). You can't get an integer out of it unless x+6 ...
October 16, 2009

physics
The flash and the sound happen at the same time, but both the light and the sound have to travel to you, at different speeds. For fun, or extra credit, you could calculate how long the light takes to travel 8000m, but it's small enough that we can ignore it, especially ...
October 16, 2009

Math
The average is the total score divided by the number of tests. All scores are integers, so the total score is an integer. The number of tests is an integer. What is the smallest total score that, when divided by an integer, would give 4.6?
October 15, 2009

english
I can think of a four letter word that begins with f. It would work even better if the first sentence were "The weather will be _____ today"
October 15, 2009

math
Given what?
October 14, 2009

pre-calculus
That's solvable easily with calculus, not sure whether you're supposed to be using it given your heading: C'(x) = 4.9(2)x - 617 = 9.8x -617.4 at its minimum, 9.8x = 617.4
October 14, 2009

geometry
Both have four sides. Both have pairs of adjacent sides equal. A kite's opposite sides don't have to be equal, but a rhombus must have all sides equal.
October 14, 2009

geometry
a) So you're looking at a Right Angled Triangle (RAT) with the two short sides being 4 and 25. What does Pythagoras say about the other side, which must be the hypotenuse? b) This is the same question, except with 6 on the shortest side instead of 4.
October 14, 2009

Programming
Glad I could help, especially in a case like yours where you clearly could do the job yourself, but just hit a snag. Good luck with it!
October 14, 2009

Programming
Given the short deadline, and that I'll be away for a while, I hacked nastily into your code, to produce something that runs all the way through, I think. I want to emphasise just how ugly this is, and that it needs a lot of work to be a worthy project! But it runs, and if...
October 14, 2009

Programming
I'll be away until tonight. How long do you have for this project?
October 14, 2009

Programming
OK, doing what I said last is really easy. Just move the two displays abve the loop, and actually draw the board instead of just returning it, like: myGame.getPrompt(); myGame.getRules(); while(myGame.winner() == 0 && !myGame.placeMarker()) { System.out.println(myGame....
October 14, 2009

Programming
I think you want a String rather than a char. Here's what I did: 1. I made a little batch file to recompile and rerun, containing javac TicTacToe.java jar cvf TicTacToe.jar TicTacToe.class javac -cp .\TicTacToe.jar Lab2.java java -classpath . Lab2 I don't know whether ...
October 14, 2009

Programming
Just home and had a quick look. My two immediate thoughts: 1. You need to write getCurrentPlayer() in TicTacToe so that you can get the whole thing to start running, from where you can get a handle on what it is doing. 2. I still don't think the instructions I/O should be ...
October 14, 2009

Programming
Nice to see you back, Tim. I'll be away from the forum until tonight, but somebody else may help in the meantime. To help them help you, you could post your thinking, given your current code. Where are you stuck? What doesn't seem to be working that you think should be...
October 14, 2009

Chemistry
After 0.6523 g of is heated, the residue has a mass of 0.3423 g. Calculate the % H2O in the hydrate.
October 13, 2009

math
two equations : n+d=42 .05n+.10d=3.85 or 5n+10d=385
October 13, 2009

if you round the number to the tens place, it is 460 if you round the number to the hundreds, it is 500 could the number be 468 and why
October 13, 2009

Math
a. (13-2)/32 = b. @1000 it had 11/32. @20000 it had 5/32. So after 19,000 it lost 6/32. It needs to lose another 3/32 to be "worn out". You should be able to see the number of miles from that.
October 13, 2009

math
Oh. If it's any comfort, I have no idea how writing sentences embodying equations could be proven, either.
October 13, 2009

math
The question wants you to figure out what number replaces X. 7 = x + 5 7 = ? + 5. What number replaces x, or the question-mark? You're going to write: x = (some digit, which is your answer) Proving is easy. Just write 7 = x + 5 down again, but this time replacing x with ...
October 13, 2009

math
"maximum: 8, range: 6" gives you your minimum number, so pencil that in, and 8 at the other end of course to make your maximum. Now, if you know what mode and median mean, you should be ready to write in some 6s, and spread about the same number of lower digits.
October 13, 2009

math
Well, we're going to need three lots of some unknown number plus 4. Let the three be bags. Since we're near Halloween, let's say some unknown number of pieces of candy get divided equally into 3 bags. Then let's say somebody adds 4 pieces to each bag. Can you ...
October 13, 2009

Math- fractions and decimals
"62 and a half" is 62.5, or 62 1/2, or 125/2. That's all fine. But you talked about a hundred chart. I wonder whether you mean what 62.5 is as a fraction of a hundred, which is the same as asking what 62.5% is as a fraction. Does your 100 chat show 50 as being 1/...
October 13, 2009

Algebra
I'm totally with you on y=8, but the best way to check your answer is to substitute the value back in. Now try y=2/3: Is |2/3+3| + 5 = 2(2/3) ? Is 11/3 + 15/3 = 4/3 ? I think you took a wrong turn at: "Now, the two equations are 3=y-5 and 3y+3=5." You can't ...
October 13, 2009

Algebra
The perimeter is two lengths + two widths, and that has to be more than 70. 2L + 2W > 70 We know that the length is 19, so 2L = 38. 2W + 38 > 70 2W > 70 - 38 Now pick a width that makes that true. There are lots of them to choose from: a million will do. :-)
October 13, 2009

Programming
OK! I suggest when you get your client ready you start a new question to keep it on the front page, since I don't think anybody looks beyond the front page much. I didn't really expect to see a response down here, but I was curious so I checked.
October 13, 2009

Programming
Tim, this forum doesn't seem to allow indenting; that's why your code didn't show. You can paste your code if you remove the leading spaces. I did get your code. But, given that, I'm not quite clear what you want to know. By "fill in the blank", do ...
October 13, 2009

Computer Science Java
A Boolean variable is a variable, like an int or a string, but whose value is either "true" or "false". Try this little lump of code, and vary d1 and d2 values, to see the effect: int d1 = 1 int d2 = 1 boolean snakeeyes; boolean doubles; boolean boxcars; ...
October 13, 2009

Math Analysis
4. "I got the square root of 7x. Is this right?" Nearly, but not quite. Careful with your sqrt signs. f(x)=sqrt(x) g(x)=6sqrt(x) f(x)+g(x) = sqrt(x) + 6 sqrt(x) = 7 sqrt(x), not sqrt(7x) 16. This is much easier on paper! Consider your constants. You have sqrt(2) on ...
October 12, 2009

math anaylsis
g takes x to x-3. That is, start with x, then g(x) will be three less. 5 -> 2, 11-> 8, 1 -> -2. Right? f squares x, so f(5)=25. Similarly, 3-> 9, 8 -> 64, and so on. f(g(x)) just means "do g on x, then do f on the result". If you start with x=5, then g...
October 12, 2009

programming
I'm also not clear what is being asked, exactly, but at least it's not just a cut-and-paste question. Steve, what exactly do you need to do, and within what terms? Do you need to create a flowchart modelling currency conversion logic using some specific software, or ...
October 11, 2009

Physics
A passenger on a bus moving with uniform velocity lurches forward when the bus stops suddenly. Explain? I do not understand this
October 11, 2009

Algebra
If it depends on something else, it's dependent. If it doesn't depend on something else, it's independent. Does the time of day depend on the air temperature? Does the air temperature depend on the time of day?
October 10, 2009

math
Do read the earlier two first. At the end of hour five, which we'll call t5, speed @t5 = 100 km/h It's been accelerating at 3km/h, so at 4 hours speed @t4 = 100 - 3 = 97 km/s and at 3 hours speed @t3 = 97 - 3 = 94 km/s You can work it back from there.
October 10, 2009

math
This is like the car problem. At the start, t0, the stone has a speed of zero. t0 = 0 m/s The acceleration is (10 meters per second) per second, so after one second the speed is 10 m/s. t1 = 10m/s After another second, we add on another 10m/s to the speed t2 = 20 m/s At the ...
October 10, 2009

math - corr
I used a shorthand that was wrong in this question, and it might confuse you. When I say t0 = 103 m/s what I should have said, to be clear, was speed at t0 = 103 m/s and so on.
October 10, 2009

math
We start counting when it's moving 103m/s. (And incidentally, that's pretty fast for a car. Formula 1, maybe?) Each second after that, it moves 1m/s faster than it was before. So if we call time by seconds, as we often do in these things, we call the start, after zero ...
October 10, 2009

ap calc
Draw the pool as a rectangle. Now draw a rectangle around that, such that each side is equally distant from the sides of the pool. This represents the sidewalk around the pool. The area of the pool is 12 * 18 = 216 sq.ft. If the sidewalk were 3 feet wide everywhere, the width ...
October 10, 2009

Algebra - oops typo
b^2 - 4ac 1 - (4)(2)(-1)
October 10, 2009

Algebra
Doublecheck the expression within the square root, and watch your signs. b^2 - 4ac 1 - (4)(1)(-1)
October 10, 2009

Finance.
Start with 10, finish with 20 after 1 year you have 10*x after 2 years 10*x*x after 3 years 10*x*x*x 10 x^3 = 20 x^3 = 2
October 10, 2009

Finance.
I just answered a very similar question from Kim right below. The method to solve this is the same, but you can make up your own numbers: say, 10,000 at the start and 20,000 at the end.
October 10, 2009

finance
I like this question :-) Let's assume interest is compounded annually. After one year, the value will be 10,477.03 * x, where x is 1 + (interest rate implicitly divided by 100). After two years, it will be 10,477.03 * x * x, because we increase it by the same percent again...
October 10, 2009

Algebra
Well done! You got it right. But I think you may have missed a turn in the simplification. The simplification is largely a matter of taste, but also laziness - the less you have to write to use your result in the next stage of a problem, the better :-) You started with: (10...
October 10, 2009

Programming & Algorithm
I'm not exactly sure what (1) is asking. General considerations? An exemplar? Anyway, a stack has only two operations: push something in; pop something out. You will need space in which to store the items on the stack. Start with the items. What data types will you be ...
October 10, 2009

Maths
Is this using current British coinage, or pre-decimalisation? There is a quite famous problem by Dudeney about this, but it uses old coinage - farthings and suchlike. The book "Amusements in Mathematics by Henry Ernest Dudeney" is available ibn Project Gutenberg, if ...
October 10, 2009

math
Magic, you need to post a new question, rather than follow on an existing thread. I'm not sure, but I think the question means that the _answer_ after subtracting 1 is 114. If so, then start by asking yourself what number leaves 114 when you subtract 1 from it. Got that? ...
October 10, 2009

marketing
Thanks for the kind words :-)
October 10, 2009

marketing
Look up what the 4 Ps are. Got that? OK. Now consider something _you_ bought recently. It's likely that it'll be easier to write about something large and unusual you bought, like a pair of skis, than something small and common, like a fizzy drink, though both will ...
October 10, 2009

visual basic
I just read your question again, and I now think that, given an input string, you want to find the first non-zero digit in it. Though again, I could be wrong. So if the input is "A046", you want "4", and if it's "0.0029x" you want "2"...
October 9, 2009

visual basic
Perhaps the most useful tip you can know in learning to program, though you won't find it in a book, is to ask for help, giving _all_ information about the problem, whether you think it's useful of not! :-) You've posted the problem code. This is good. You haven&#...
October 9, 2009

System analysis
The hardware vendor will say it's a software problem. The software company will call it a hardware problem. The department manager will have somewhere else to be. The sysadmin/BOFH will sigh and mutter "PEBKAC" as he walks past. The experienced project manager ...
October 9, 2009

math
This one's kind of pretty. I first thought we'd be into sin and trig country, but we don't have to. But you have to see it in a diagram. Draw lines for the lamppost and the woman, and a line from the top of the lamppost just over the woman to the ground. You should...
October 9, 2009

Alg
I don't think (2z)^(1/2)/4z^4 can be correct, since y has disappeared. Take it in steps, by distributing th power: (y^(1/4)*Z^4)^(-4/5) = (y^(1/4))^(-4/5)(*Z^4)^(-4/5) Now, what's the rule for raising powers? As for (3-2SQRT2)(SQRT6-5) I don't really get it to be ...
October 9, 2009

Math
You've done the hard part; you're almost there! You just lost sight of the simple bit. x = 2/(2a+1) we need to find a when x = 10 10 = 2/(2a+1) Now find a
October 9, 2009

algebra
y=mx+c m= -1/6 y=-(1/6)x+c The point (-6,9/7) must be on that line: use it to find c by plugging in x and y like 9/7=-(1/6)(-6)+c So what's c? So now we have the equation of the line, we need the value of the point on that line where x=12. Plug in 12 instead of x in the ...
October 8, 2009

Physics check
A person has a reasonable chance of surviving an automobile crash if the deceleration is no more than 30 "g's" (recall that g = 9.8 m/s2). Calculate the force, in N, on a 68 kg person accelerating at this rate. 30"g" x 9.8 294 ms^2 f=ma 294x68 =19,992N
October 8, 2009

visual basic
I didn't verify your code, but I see the general way to do it. Suppose you have user(1) = "vsu1"; password(1)="123456" user(2) = "jim"; password(2)="abcdef" now, after the swap above, you have user(1) = "jim"; password(1)=&...
October 8, 2009

[math]
You have the right idea, but watch your sign: 3x-2y=7 Subtract 3x from both sides: -2y = -3x + 7 Divide by -2 y = (3/2)x -7/2
October 8, 2009

equations
Sign dropped? Doesn't y+x=-5 rewrite as y=-x-5?
October 8, 2009

algebra
By solving it graphically, I presume the question means draw the graph, and read off the answer from the point where the lines cross. To do that, you need to draw each of the two lines. Start with the first one: y-x+4=0. You need to find two points on that line, then use your ...
October 8, 2009

physics
Aaach. In (a) I meant "The boat actually ends up at the point (0,-4) after 3 hours. " Sorry for the confusion.
October 8, 2009

physics
There are a couple of ways to consider this, and I'm probably mixing them, so check my sanity as well as my thinking! I'm not at all sure I've got this right. And draw a small sketch of the points; it makes a whole lot more sense that way. (a) Consider the harbor ...
October 8, 2009

Math
How do you convert C to F? Multiply by 9, divide by 5, then add 32. Multiply 1.1111111... by 9, you get ---- which is equivalent to (it may look nearly the same as, but it is the same) ---- Divide that by 5, to get ----- Now add 32.
October 8, 2009

Math
Um, possible typo there? If the cards are drawn _with_ replacement, the first card is back in the deck when the second is drawn, and the probability of the second being a diamond is again 13/52?
October 7, 2009

math
First, draw your triangle so you can see what you're doing. The short side, 12, will be opposite the small angle, 30. We know that the sin of an angle = opposite over hypotenuse. The angle is 30, and we can look up sin(30)=0.5. So opposite (which we know is 12) over ...
October 7, 2009

math
Consider the line tangent to y^2=4x. It has m = x^(-1/2). At 1,2, that's m=1, so y=x+1. The circles are tangent to this line, so a perpendicular through (1,2) joins their centres. That'll be y=-x+3. So to get our centres we're looking for two points with a distance...
October 7, 2009

The counting principle is oddly-named, since it mostly involves multiplying :-) It just means that if you can do the first thing x ways, and then in the next step you can do that y ways, then overall you can do the whole thing in x * y ways. Consider a two-digit PIN. How many ...
October 7, 2009

math
For a rectangle, you need to have sides A and B wide and long. Then you multiply A and B to get the 50 players. This is the same as asking how can 50 be factored into two factors (which don't have to be prime). Start with the prime factors. 50 = 5 * 10 = 2 * 5 * 5 Um. ...
October 7, 2009

algebra 2
An inverse just undoes what the original function did, so you can get it by doing the opposite of what the original functtion did, in reverse order. g(x) tells you: multiply by -6, then add 5. Its inverse will tell you: subtract 5, then divide by -6. Example: g(2) = 2*-6 + 5...
October 7, 2009

maths
I don't see a short-cut. Could this just be division practice? I make it two such numbers of 24 possibilities, one of which is 4186, and the other is predictable from that because 8 mod 7 = 1, and the equation (1000a + 100b + 10c + d = 0 mod 7) works out to (6a + 2b + 3c...
October 7, 2009

math
Forget the halfway for a minute. From the point she fell asleep, she slept twice as long as the rest of the flight after waking. Does that smell like 2/3 + 1/3 to you? Back to the halfway bit... She slept 2/3 of the second half of the flight. She slept 2/3 of half of the ...
October 7, 2009

Math
You're wrong about one thing; you _do_ know how to do it. You just did it :-)
October 7, 2009

math
You multiplied by -1/4, I presume: -4x>1/11 -4x (- 1/4) > 1/11 (- 1/4) x > -1/44. That's what I get, too!
October 7, 2009

algebra
Let's take the first one. We know that any line can be expressed as y = mx + c First we plug in the m given: y = (2/3)x + c. Now, we know that the point (3/2, 9/5) is on this line, so we can substitute these values into our equation to find c: 9/5 = (2/3)(3/2) + c 9/5 = 1...
October 7, 2009

Math
You typed both 81,700,00 and 81,700,000. I will assume you meant the second, because of the placement of the commas. So Standard form 81,700,000 = 81.7 * 10^6 = 8.17 * 10^7 In scientific notation, we put only _one_ digit before the decimal place, so you will never see 81.7 x ...
October 7, 2009

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