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Math / Science

The Math / Science topic primarily includes discussions of mathematics, physics, statistics and economic analysis, but also biology, chemistry and other sciences.

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If I remember correctly hen I was sitting in math classes a long time ago, there was a simple rule to establish the number of decimals needed to keep accuracy.

My problem is that I have a number of units and a price (resulting in a market value).

For example, if I have 3,976,796.834 units and the price is 10.052580533713, the resulting MV will be 39,977,070.4400.

Now I need to define how many digits I will need to keep (and I cannot keep 12) in order to keep the most accurate value.

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A school has been able to acquire a number of Smartboards for classroom use.  Math teachers and science teachers are the majority of the recipients.  Does anybody know of a good trainer that can show these teachers uses within a school setting?
What is the answer for this question
Hi,  I am looking to design a profit sharing scheme that would take into account the job level of the employee, the performance of the geographic region, and the individual performance level.  The first can be a number between 1 and 7 or a dollar amount, the second will be the achievement of projected profit, and the third will be a number between 1 and 5.  Is there anyway to calculate a final contribution without making it the percentage of a cap?  The total pool for each geographic regional will be a straight percentage of profits.

i.e. 15% of profits might be 10 million for ease of calculation.  For thirty employees, is there some formula that will reward each employee a portion of that 10 million based on their job level, achievement of projected profit, and ind. performance???

Thank you!
A dice is rolled until the game is stopped. The game stops when there is a 4,5, or 6. For every number 1,2, or 3 the score increases by +1. If the game stops with a 4 or 5, the accumulated score is paid. If the game is stopped with a 6 then there is no payoff. What is the expected payoff of the game.

I thought about it as follows:
The probability that the game stops with 4 or 5 is 2/3. The probability that payoff is 0 is 1/2 that is I get 4 or 5 in my first throw. The probability that payoff is 1 is (1/3)*(1/2) i.e. I either get 1,2 or 3 in my first throw and 4 or 5 in the second.
The probability that payoff is 2 is (1/3)^2*(1/2) i.e. I either get 1,2 or 3 in my first and second throws and 4 or 5 in the third.
Then the expected value is :
2/3*sum of((1/3)^n*(1/2))*n ,where n ranges from 0 to infinity.

However, this is not giving me the correct solution which is 2/3. Also, how can I solve it using recursion?

M.S. Steel ingot size is defined by having one bottom square base of side 3.5" and top square base of side 4.5".Both base are connected by length equal to 58". Basically it's a tapered ingot.
Dear experts:
Can someone please help me clarify the criteria to determine n and r in Permutations and combination. I think I am solving these problems by thumb rule rather on a proper understanding.
Below I have listed a few questions along with solutions where r is greater than n or i am not sure how allocate n ways to r blanks. Please help.

We know that the number of ways of filling up r blanks with n dissimilar things is nPr. The first blank can be filled with any one of the given n things in n ways.
Below I have a few examples:
Q1 In how many ways can 7 women go to 9 restaurants?
      1      2      3      4      5      6      7      8      9      
R blanks                                                            
N ways                                                            
The Permutation given is 97
Clarification: How do I determine which is n and which is r?

Q2 In an examination paper there are 8 questions each with 4 answer choices and 5 questions each with 2 answer choices. The no. of ways of answering the question if all the 13 questions are attempted is?
The Permutation given is 48 * 25
Clarification: How do I determine which is n and which is r?
Q3 In how many ways can 5 letters be posted in 6 boxes?
The Permutation given is 65
Clarification: How do I determine which is n and which is r?

Please help. Thank you
X = 1   2
       3   4

y = 3   1
       4   2
how can i convert x to y????
It is for a science project we just don't have any weighing scales to test it ourselves
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How much more will the cost be for a wager on V5 compared to V4 when adjusting for difference in probability, price per unit and track's deduction?:

For V5 (a type of wagering on harness racing where you should pick the winner in 5 races), the probability to pick the winners in the five races is 12 times more difficult compared to for V4 (1/248832 divided with 1/20736; (12x12x12x12x12)/(12x12x12x12)), which means you need to spend 12 times more units on V5 to achieve the same probability. However, this should be adjusted first for price per unit, which for V4 is 2 SEK and for V5 is 1 SEK, so the adjustment becomes 12 x 0.5 = 6.

The final adjustment is for the racing track's deduction, which for V4 is 25 % and for V5 is 35 %.

Is this correct?:

6 + (0.1/0.25) = 6.4

Which means in order to compensate for lower probability in V5 compared to V4, and for difference in price per unit (V4: 2 SEK; V5 1 SEK) and difference in track's deduction (V4: 25 %; V5 35 %), I need to spend 6.4 times more units/money on V5 compared to V4 so that I in the end have the same probability to win on my wager on both V4 and V5, provided that the payouts on both the wagers are the same.

Or do I get it wrong? Is it that the payout on V5 needs to be 6.4 times higher than on V4 in order to compensate for the difference in probability, price per unit and track's deduction?
We have 12 players, and we would like to set up a 6 team round-robin tournament for a few different backyard games. We'd like to play as many different backyard games as possible with these 12 players (6 teams of 2 players), while ensuring that no two players get matched up more than once across the different games.

Looking for a grid of as many of these unique matchups (round robins) as mathematically possible.


Players: 1 - 12
Teams of 2
As many combination of 6 teams as mathematically possible while ensuring no two people end up together on a team more than once
Imagine you have a dataset of rowers. You have X variables such as weight, benchpress, deadlift, squat, nutrition, etc. You also have each rower's lap time.

Now, let's say for a given rower, you want to optimize her lap time, but you can only train along ONE DIMENSION. How would you identify the best attribute to optimize?

I thought about a grid search, but that seems awful. Which family of machine learning algorithms would be best for this type of problem, and how would you attack it?

Thanks a million!
I am trying to rotate an object and get the following error message: 1119:access of possibly undefined property Math through a reference with a static type class. Thank you for your help

 here is the code


stage.addEventListener(MouseEvent.MOUSE_MOVE, FollowMouse);
function FollowMouse(event:MouseEvent):void
      var SideY:Number = mouseY-circle.Y;
      var SideX:Number = mouseY-circle.X;
      var Rad:Number = Math.atan2(SideY,SideX);
      var Deg:Number = Rad * 180/Math.PI;
      circle.rotation = Deg;
I have a client who has an issue getting the LINEST() function to work for them.  This is my first time using LINEST(), and what seemed, at first, to be straightforward has deepened considerably in levels of complexity.  I am an accomplished VBA programmer, and I feel the best way to give the client what they need is to duplicate the equation in VBA to calculate the slope (m) when there are multiple X Axes.  When only one X axis exists, I have validated LINEST against my own independent calculation, as shown by the equation below.

slope (m) calculation for single X Axis
I am looking for a similar equation I can apply, given 2 or more X Axes.  Reproducing the underlying query in VBA will make for a much more versatile function, capable of calculating LINEST in a more wide-ranging set of circumstances than Excel currently allows, thus meeting my client's requirements.  For those not familiar with LINEST(), I have included a couple of sites that have given me the best start on solving the problem.  The office support site provided the equation, as shown above, which gave me a reliable means to have an independent check against the Excel function on a single X axis.  Every site I've seen thus far provides the LINEST() equation for multiple X Axes, but nowhere have I seen a more nuanced formula that tells me what Excel is doing to derive that number.  That's my missing piece.

Thanks, in advance, for your support.  ~ Peter Ferber
The following problem refers to strings in A, B, ..., Z.

How many four-letter strings are there that begin with O ?
I heard gastritis and heartburn can be solved by ingesting alkaline substances.
Alkaline plants supposedly containing alkaline substances can be ingested to lower the pH value in the stomach due to stomach acid.
I'm trying to extract alkaline substances from plants using simple boiling extraction.
Thus, I tried to extract alkaline substances from a alkaline plant, dandelion, in ethanol and ethyl acetate solvent for 10~15 minutes.
The solution was filtered with carbon black for decolourization, but it didn't show alkaline colour with universal indicator.

So... I've got some questions to ask

1. Is dandelion alkaline?
2. If it's alkaline, is it possible to extract alakline substances or alkaloids from the plant?
3. If dandelion is not alkaline enough, then could there be any othe ralternative plant or food that can be extracted alkaline substances?
4. Is alkaloid alkaline?
5. What are the alkaline substances coming from?
6. If the simple boiling extraction doesn't work , is there any other ways that I can extract alkaline substances from the plants?

Could you explain in high school level.
I hope this forum can also help regarding electricity science.
Need to purchase a few single cells of lipo and ni-mh battery types >> high drain >> for airsoft purpuse, and rc!

1. Would like to get anykind information to get them from any Europe dealers, wholesalers,distributors, etc?
2. Or, name of a few manufacturers companies?

Thanks in advance...
I wish to extract info from a land registry file - see info on this link.

I have a UK land registry .gml file downloaded from their site

I have installed QGIS and have managed using the menu item FILE / IMPORT VECOR DATA / COMMON IMPORT FORMATS browsed to the .gml file and opened it but all I see is View1 ( attached ). I can zoom to produce View2 & 3 ( also attached )  but I can't see how I can reveal the Polygons referred to by the Land Registry.
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Due respect sir,
The we questions is that

(A×B.C)(a×b.c)=|A.a.      A.b.      A.c.  |
                           |B.a.        B.b.     B.c.  |
                           |C.a.       C.b.      C.c.   |

Sir as soon as possible plz send the solution my mail

                   Thank you
                  Your student
Scenario: bins are taken out once a week from a storage area to another location more than 20 meters away. I want to know if the bins have NOT been taken out at any given time each week.

eg if the bins are tagged and the storage area has a receiver, the receiver can tell me if the bins are in or out of storage.

I would like to tag around 4 bins only. What cheap and simple tagging solutions exist?  

I would like the receiver to connect to wifi so i can check the status remotely. The tag on the bins should be small and discrete, so as not to encourage vandalism or theft. They should also be very low power so that batteries, if the tag needs them, would need changing at most once a year. Perhaps a magnetic solution would avoid need for batteries on the bins.

The position of the bins in the storage area is not precise but would not vary by more than 2 meters.

If ax²+2hxy+by²=c²,verify that dy/dx.dx/dy=1
consider the subgroup of s4 given by G={(123),(134)}
1 what is the order of G
2 what are the orders of the elements of G, and how many elements of each order.
3 what are the orders of the subgroupsof G Give an example of a subgroup of each order.
The curve on the tab "Curve fitting graphic" in the Excel "Distansomräkningstider" attached here is almost perfect. It is only the last part that is pointing too sharply upwards. It should be more flattened out (but never turn townwards, always continue to pointing slightly upwards) from around 2500 metres or 2600 metres, which seems to be a "breaking point" for two different curves.

The context is harness racing track times for different lengths of the races with the purpose of calculating re-calulation coefficients for different lengths of the races. Index is 2140 metres (x). The software I use is CurveExpert. I received help here at EE earlier at this thread:

Is there any online tool where I can enter x and y values to get a curve diagram displayed, and then enter more x values to get exact y values calculated?

In essence, this graph consists of 2 curves, and they cross each other at around 2500 or 2600 metres. The first curve is more favouring the speed of the horse (shorter distance, which means the horse is able to run much faster due to a short distance where strength and stamina is not required), whereas the second curve is more favouring the strength, or stamina, of the horse (longer distance, which means the horse can not run so much faster the more the curve moves to the right and the distance gets longer and longer).

My reliable five values I have now are these:

x=1640; y=0.913999
x=2140; y=1
x=2640; y=1.048999
x=3140; y=1.110999
x=4000; …
I'm not sure if this is the right place to try asking this - But here goes anyway

Using a sampling pump I want to push water through a ½  or ¾  inch Sch80 PVC pipe with enough pressure to traverse 20 feet vertical and 600 feet horizontal in a minute or less. This is next to a free flowing canal. I want to sample 600 feet upstream to prepare for what will be coming in the intake. The canal runs about 15 minutes to cover the same distance . This give me a 14 minute look ahead.

I calculate that it will take about 150PSI (using 1.8 Hp) in ¾ inch pipe and about 230 psi (using 1.25 Hp) in ½ inch pipe.
That gives me about 10 ft/sec.

2 questions:
  1. I used math I am not familiar with so are my calcs even in the ballpark?
  2. Will 10 Ft/sec be a problem for PVC piping? I read somewhere that over 5ft/sec will be noisy (which is OK) and make the pipe wear badly (which is not) .

Hope you can help.

Math / Science

The Math / Science topic primarily includes discussions of mathematics, physics, statistics and economic analysis, but also biology, chemistry and other sciences.