Friday
August 28, 2015

Posts by jim


Total # Posts: 1,508

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

7th grade math
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

algebra
Oops, typo. In case you're confused, I meant "One way to approach it is, as you say, to add -5x to both sides..."
October 7, 2009

algebra
When you have an equation with just x and y terms, you're looking at a straight line. One way to approach is it, as you say, to add -5 to both sides, and then divide across by 2, so that the LHS just contains y on its own. Then you have it in the form y = mx + c, and you ...
October 7, 2009

algebra
I think you mean (12-8)(7-4)^3 Just checking, because an extra bracket around like ((12-8)(7-4))^3 would give a different answer. Brackets first. Then powers or roots. Then multiply or divide. Then add or subtract. First do the arithmetic inside the brackets: (4)(3)^3 Now ...
October 7, 2009

Algebra
To find the y-intersect, you can just set x=0, and see what's left: y + x = -10 y + 0 = -10 y = -10 So (0, -10) is your intersect. This is a straight line, so all you have to do is find two points, and use a ruler to draw a line through them. Let's find the x-intercept...
October 7, 2009

Math
Just start at the beginning and think it through choice by choice. There are 11 to choose from. How many can you choose? 11. Now you've seen one. Choose another. How many do you have to choose from? 10, 'cos you've already seen one. So how many ways can we choose 2...
October 7, 2009

vocab
On the same assumption, I see that "chosen" works as well.
October 7, 2009

AP Stats
Well, $115 is exactly one SD below the mean, so that's handy. A useful guideline is that, moving left to right, over 2SD covers the first 2%; 2-to-1 SD is another 14%, bringing you up to 16%, and 1-to-0 SD covers another 33%, bringing you to the mean at 50% (not quite, ...
October 6, 2009

math - equivalent expression
An example of the distributive property: 3 * (1 + 2) = (3 * 1) + (3 * 2) x * (a + b) = (x * a) + (x * b) or x(a+b) = xa + xb Where the operators are like this, you multiply the figure outside the brackets into each of the symbols intide the brackets separately. You can also ...
October 6, 2009

GEOMETRY
Each lilt contains at least one distinct pair. There must be exactly one lilt containing each possible pair. Which axiom number is that? We know that L1 contains {A, B}. Write out the pairs you can make from A, B, C.
October 6, 2009

GEOMETRY
That allcaps is a bit hard on the eyes. If you want people to read your message, do tone it down and type normally, please. From 2) spoof contains at least two purrs. Call the first two A and B. From 4) there exists exactly one lilt containing them, therefore 1. is proved. ...
October 6, 2009

math
My bad, Ellie and Reiny, on the second one. My thinker slipped a cog, and I considered y = 1/|11-9x|-6 rather than 1/|11-9x|-6=0. Reiny is correct, of course!
October 6, 2009

math
Sorry, Ellie, I'm not quite sure what it is you have to do with them - graph them? specify a range for which they are defined, or true in the first case? make a table of values? Anyway, I'll talk a bit about them. The first one says -2 * x^2 < 30. Now, this one is ...
October 6, 2009

arithmetic
This sounds awkward, but is actually easy. Consider the number 400P. It must end in zero - actually, it must end in 00, since it has 100 as a factor. Therefore its cube root must end in zero. Check this for yourself: the last digit of a cube can be determined by the last digit...
October 5, 2009

AP Calculus
You're very welcome, Bri. And do look up _why_ that is true sometime. It's quite neat.
October 5, 2009

AP Calculus
You don't actually have to know the whole function to get its value at one point, if you have other useful information. You can - and should! - look up the background to "Leibniz's law", but it says that f(x)=g(x)h(x) implies f'(x)=g'(x)h(x) + g(x)h&#...
October 5, 2009

Help with deductive reasoning
Let's take the first one. You can make a syllogism if you have two statements like: (1) If A, then B _and_ (2) Rover is A (3)_then_ you can say that Rover is B Now: (1) If a dog eats Superdog Dog Food, he will be happy. (2) Rover is happy. What is "A" here? it&#...
October 5, 2009

Prorgramming in Java
I'm not a teacher in this forum, but that's kind of a big lump of a problem just to throw out there and expect help with. You'll probably get more useful help if you break it down into tasks - starting with the writing of the CatalogItem class, I suspect - and then...
October 5, 2009

maths
regina, in the second part, you ask about the graph. When I was doing this kind of thing, I always used to calculate the x and y intercepts, and then just draw a straight line between. Nowadays there is "Wolfram Alpha" wolframalpha you-know-what on the net
October 3, 2009

math
The first one is either a typo or a trick, since no number of cm^2 make a litre. Was ir cm^3? There are 1000 cm^3 in a L. By "simplify", I presume the question means convert to one unit - either pounds or ouncez. There are 16 oz in a lb, so one pssible answer is (10...
October 3, 2009

math
Assuming the question was "Find the value of the digit 5 in 35,791" you are absolutely right!
October 3, 2009

Statistics
Since the flight is always fully booked, we can say that the luggage weight's mean is 8000 and the SD is 2000. We're interested in the number of flights that is more than (300 / 2000 =) .15 SD above the mean. Now we go to a z-score table - Google will provide, if you ...
October 3, 2009

maths
Profit then 30M. Profit later, 210M. Change in profit is obviously 180M, right? OK, so that change is over how many years? 1992 to 1998 - 6 years. Profit changed by 180,000,000 over 6 years, so on average it changed $180,000,000 / 6 per year.
October 3, 2009

algebra
When you see an inequality, and most other equations, with one variable, your first job is usually to add, subtract, multiply, or divide, to get the variable on its own, isolated from the numbers. Just remember to do the same thing to both sides. This one has three sides, but ...
October 3, 2009

Computers
Ouch. Typing too fast. Should test in that else that l1 hasn't exceeded 10. But you should get the idea.
October 1, 2009

Computers
This is one of the classic workhorse situations of programming, a sort-merge, used just about everywhere. You sort two lists, then merge them. The basic idea is this: Establish a pointer to the first (lowest) entry in each list, then Loop while any entries unmerged: 1. Compare...
October 1, 2009

Algebra ll
Slope-intercept form y=mx +c where m is the slope. You are told that the slope is -4, so the equation muct be like y = -4x + c That rules out one of your choices. Now, of the other two, the equation must be true for the point (1,2). So which of these is true? 2 = -4 * 1 + 6 2...
September 30, 2009

math
Think about the line y=-1. What does it look like? It's all the points where y is -1: (0, -1), (2, -1), (-2000, -1)... so it's a line straight up and down. Any line perpendicular to is must be straight across, so it must be of the form x = something, where all the ...
September 30, 2009

8th grade math
Write down the prime factors of each. Look at all the factors, of both numbers, together. The LCM will be the smallest set of this list from which you can make either of the two original numbers. Example: 30 = 2 * 3 * 5 24 = 2 * 2 * 2 * 3 So we have 2, 2, 2, 2, 3, 3, 5 to ...
September 30, 2009

math
Yes. You want the two big digits in the tens place for the big one, and you want them in the units place for the small one. So 41 + 32, or 42 + 31, and 14 + 23 or 13 + 24 are the best you can do.
September 30, 2009

C Programming
Oops. I got the bracket messed up in the pseudocode and left a <= instead of a < in the while.
September 30, 2009

C Programming
I doubt that it was too long, considering the programs you and I posted earlier. Maybe indentation? You could try something like a do loop around your validation, of the form: do } {get heading and display error message if necessary) } while (heading is not valid) e.g. /* ...
September 30, 2009

Math
I don't know what polygons you drew, but consider this: no matter what path you took, if at any point you are turned to the left of where you started, you must have turned through 90 degrees (plus some integer number of full turns); if at any point you are turned backward ...
September 29, 2009

physics
A Newton is 1 kg * m / s^2. The force here is 20 kg * 5m / s^2. You should see it clearly from there.
September 29, 2009

Algebra 1
Yes! That's what I get, too.
September 29, 2009

physics
Start by calculating the acceleration of the plane as it moves from rest to take-off. It gets up to 80 m/s in 35 seconds, so its acceleration is 80/35 m/s^2. Now you can just plug in the formula for distance travelled under acceleration = ut + 0.5at^2. Initial velocity u is ...
September 29, 2009

C Programming
Your problem is that you are always doing a CtoF or FtoC conversion, even when it's F to F or C to C. You need to take both choices into account in your conversion logic, not just the one you're converting to. Actually, your approach is a bit convoluted. It can be done...
September 29, 2009

math
I'm not sure I know what the question is asking. I'm guessing you have to fill in the numbers equal in distance all the wat between 1562 and 1874. There are five numbers missing, so there are six gaps between. What size must a gap be? Well, there are 6 gaps of equal ...
September 28, 2009

Stats
Sorry about my mental arithmetic error. :-) So 9 months is 2.12 SD. so 1SD is 4.25 months. 1.28 SD is then 5.44 months from the mean, so the mean is 22 - 5.44. Check: working it the other way .84 is 3.57 months, so the mean is 13 + 3.57. Do those agree? Yes, our mean is 16.57...
September 27, 2009

Stats
90% is 22 months, is 1.28 SD from the mean. 20% is 13 months, is .84 SD in the opposite direction from the mean. Thus, a difference of (22 - 13) months is equivalent to to (1.28 - (-.84)) SD.
September 27, 2009

Stats
Given the mean and atsndard deviation, you can find the score for an area under the curve, but working backward, given two percentiles and scores, you can work that in reverse. Reading off the numbers from a z-table (I hope you don't have to work it out from the equation...
September 27, 2009

math
I'm not sure what the question is, but if k + 9 is greater than 12, then what is k greater than? Pretend k is zero. Is k + 9 > 12? Pretend k is 7. Now, is k + 7 > 12? So what must k be greater than? Another way to approach the inequality is to add or subtract the ...
September 27, 2009

Advanced Functions - urgent
This appears to be from an intro to calculus course. "instantaneous rate of change" is equivalent to slope, so the questions A and B become "what is the slope of the function" at these points. Have you done differentiation? If you have, you should be able ...
September 27, 2009

Algebra 1A
evaluate (-8b)^2 and -8b^2 when b=10. (-8b^2)= -8b^2=
September 27, 2009

FIN 200
Collins Office Supplies is considering a more liberal credit policy to increase sales, but expects that 9 percent of the new accounts will be uncollectible. Collection costs are 5 percent of new sales, production and selling costs are 78 percent, and accounts receivable ...
September 26, 2009

pre calculus
The first pair is very very easy. Remember that a line that passes through the origin must be of the form: y = mx since the intercept is zero. You are told that this line passes through the origin and that the point (-1, 5) satisfies the equation. You should be able to write ...
September 23, 2009

C programming
Oops, I meant 6 possible answers. While I'm here, remember strcpy puts the value into the string, and strcat appends it to the end of the string. Remember to be sure to declare result to be a char field (more than) big enough for what you're going to put in it.
September 23, 2009

C programming
It's not too hard. Think that there are only these possibilities: Positive X, Positive Y Positive X, Negative Y Negative X, Positive Y Negative X, Negative Y and zero x and / or y OK, so your program will output one of 5 possible answers. You take in two numbers, call them...
September 23, 2009

math
Take any digit, say 2. Multiply it by 10. What's the last digit? Multiply that by anything else. What's the last digit?
September 23, 2009

math
It's a very simple pattern, really. :-) Think what happens to the last digit of any number when multiplied by ten.
September 23, 2009

calculus
Oops, I didn't calculate the intercepts. My bad.
September 23, 2009

calculus
I wonder if the second question isn't a little more mean and evil than that? :-) The parabola is upturnd, symmetrical around x=0, like a rounded hill. A tangent to that parabola that forms a side of an equilateral triangle as described would be of the form +/-sqrt(3)x + c...
September 23, 2009

math
Answered below
September 22, 2009

math
Answered below
September 22, 2009

college math statistics
I agree with you on A and B. C: You know that P(over 65) = .12 and the question states that 40% of this group take 5 or more prescriptions. Can you take it from there? D: First figure: 1) How many people under 65 use 5 or more prescriptions and 2) How many people over 65 use 5...
September 22, 2009

math statistics/probability
Answered above
September 22, 2009

Algebra 1
Call the number of miles x. Every trip costs at least 1.50, so we can call that a constant that we add to every trip. It is also the only fare if the trip is two miles or less/ In addition to that, every trip over two miles costs an extra 1.20 * x, except for the first two ...
September 21, 2009

algebra
There is no single "solution" to this equation. You can see that easily: 9 + 3 * 1 = 12 6 + 3 * 2 = 12 so this does not specify a unique x or y, but for any given x, there can be only one y. In fact, it specifies an infinity of (x, y) pairs, that, if you graph them, ...
September 20, 2009

math
I'd go for "negative y-values are reflected in the x-axis", but my terminology may be out of date.
September 20, 2009

Math
Apart from the subject, that equation isn't going to peak for x > 0. I think you may have an error in the question.
September 20, 2009

Math
First, 5:00, 120 minutes, is right. You can do this without algebra. In fact, algebra would only complicate it. In the jargon, 120 is the lowest common multiple (LCM) of 40 and 60. That means that it's the smallest number that both divide into evenly. 40, 80, 120 60, 120 ...
September 20, 2009

Physics - heat
1 caloris is the amount of energy needed to raise the temp of 1g or water 1 degree. So if it raises 50g by 28 deg, that's how many calories? OK, so we know how many calories affected the water, but we are also told that the burning was only 40% efficient, which means that ...
September 20, 2009

physics
You're very welcome, Mary. Sometimes, just sometimes, a picture, or graph, or video, is worth much more than a thousand words.
September 20, 2009

physics
When the rivet goes in, let's say its length is L. As it cools, it shortens a little, so its length is now L-delta(L). But it's holding the two plates, so as it shortens, it pulls them together just a little, by the amount delta(L). What you're thinking is that its...
September 20, 2009

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