Monday

August 31, 2015
Total # Posts: 1,994

**maths permutation and combination**

Thanks
*April 13, 2008*

**maths permutation and combination - answer pls check**

Pls check if my answer is correct 26C3*10C4 =26!/(26-3)!3! . 10!/(10-4)!4! = 26*25*24*23!/23!*6 . 10*9*8*7*6!/6!*4*3*2*1 =15600/6 * 5040/24 =2600*210 =546000
*April 13, 2008*

**maths permutation and combination**

Your password for a given website is made up of three letters followed by four numbers. Find the number of possible passwords if there are no restrictions on what three letters and what four numbers can be used.
*April 13, 2008*

**critical thinking**

thanks for the correction
*April 13, 2008*

**critical thinking**

n 1976 a powerful earthquake hit the city of Tangshan, China. Scientists had failed to predict the earthquake. If people had paid attention to the unusual animal behavior that preceded the earthquake, however, they would have known it was coming. Animals can often sense an ...
*April 13, 2008*

**critical thinking**

In 1976 a powerful earthquake hit the city of Tangshan, China. Scientists had failed to predict the earthquake. If people had paid attention to the unusual animal behavior that preceded the earthquake, however, they would have known it was coming. Animals can often sense an ...
*April 13, 2008*

**Chemistry**

Liquid Chromatography lab: Why is it important that the solvent level not drop below the upper level of the stationary phase once the stationary phase is packed in the column. is it because if the stationary phase dries out, then the mixture will be permanently absorbed
*April 13, 2008*

**math riddle ALGEBRA WITH PIZZAZZ**

He burned his lips on the exhuast pipe
*April 6, 2008*

**biology**

Hey can you help me out with these questions? What is the separation of homologous chromosomes during Anaphase I of meiosis called? What is the animal secretion serving as communication between members if the same species? Thanks?
*April 5, 2008*

**math**

The question is; identify the center and the radius of the circle in this equation. 3x^2 - √ 3x + 3y^2 - y + 1/12 = 0 I ended up getting C:(√ 3/6, 1/6) and R: √ 3/6
*April 4, 2008*

**Math**

I am thinking about going back to college and taking online math classes. I am eligible to take either financial mathmatics or contemporary math. But I am not really sure what the difference is between them. Is there one that is more easy than the other?
*March 29, 2008*

**math [basic trig]**

Sam and Markus are standing on level ground 100m apart. A large tree is due North of Markus and on a bearing of 065degrees from Sam. The top of the tree appears at an angle of elevation of 25 degrees to Sam and 15 degrees to Markus. Find the height of the tree.
*March 25, 2008*

**Math**

I seem to be having problems setting up Linear Programming questions. For example: Kustom Kars does van conversions. The Custom conversion required 15 hours of shop time, 8 hours of painting time, and 1 hour of inspection time. The Deluxe conversion requires 12 hours of ...
*March 23, 2008*

**chemistry**

A reaction rate increases by 60.3% when the temperature is increased from 21.5 to 35.6°C. Calculate the activation energy (in kJ/mol) for the reaction.
*March 23, 2008*

**chemistry**

how did you get No and N?
*March 23, 2008*

**chemistry**

Sulphuryl chloride, SO2Cl2, decomposes according to the following first-order reaction: SO2Cl2(g) ¨ SO2(g) + Cl2(g) At a certain temperature, it is observed that it takes 147 minutes for 23.0% of the sulphuryl chloride to react. Calculate the half-life for the ...
*March 23, 2008*

**Biology, Please Help!**

Why is it important that ions being transported across a cell membrane be shielded from the interior of the lipid bilayer?
*March 19, 2008*

**Biology: Cells**

Why is it important that ions being transported across a cell membrane be shielded from the interior of the lipid bilayer?
*March 19, 2008*

**Language Arts**

I need an iambic pentameter poem that sounds like guy has written it. Also to be about school.
*March 18, 2008*

**science**

please explain the difference between pitch and volume in sound
*March 17, 2008*

**calc- thanks!**

is this series convergent the series from n=0 to infinity of (n^2+1)/(n^3+1) i said it converged at n=1
*March 17, 2008*

**calculus**

does this series converge, and if so is it absolutely convergent? the series from n=1 to infinity of ((-1)^*n+1))/n^4 I found that by the ratio test it was inconclusive, so no abs. conv is this right? and how do i know if it is simply convergent?
*March 17, 2008*

**calculus**

does this series converge, and if so is it absolutely convergent? the series from n=1 to infinity of ((-1)^*n+1))/n^4 I found that by the ratio test it was inconclusive, so no abs. conv is this right? and how do i know if it is simply convergent?
*March 17, 2008*

**pre-calculus**

given that c is the logarithm of x in base a, and d is the logarithm of x in base b, find the general statement that expresses the log of x in base ab, in terms of c and d. [*subscripts not included: a,b,ab] loga_x=c ; logb_x=d ...logab_x = [in terms of c and d]
*March 16, 2008*

**chemistry**

what is the hybridization at O with the lewis structure of 2-propanone?
*March 13, 2008*

**college calculus**

how do you intergrate sqrt((1+((1/4)/(4-x^2)))
*March 11, 2008*

**college calculus**

how do you integrate sqrt( x^2 - (x^2)(e^(-2x)) )?
*March 11, 2008*

**chemistry**

is calcium carbonate a base? (whats its ph?)
*March 6, 2008*

**calculus**

integrate (x+2)/((x^2+2x+4)^2) the usual partial fractions dont work???
*March 3, 2008*

**Chemistr repost**

Determine the cell potential (in V) for a platinum electrode in an acidic solution of 0.004M H+(aq), 3.226M ClO4-(aq) and 4.445M ClO3- (aq) ions, coupled to a gold electrode in 3.238 M Au3+ (aq) at 307.10 K. Im confused about the mulitple molarities given for the platinum ...
*March 1, 2008*

**Chemistry**

Determine the cell potential (in V) for a platinum electrode in an acidic solution of 0.004M H+(aq), 3.226M ClO4-(aq) and 4.445M ClO3- (aq) ions, coupled to a gold electrode in 3.238 M Au3+ (aq) at 307.10 K. Im confused about the mulitple molarities given for the platinum ...
*March 1, 2008*

**College Calculus**

Could someone explain how to distinguish improper integrals in non-mathematical terms so I may understand? Thanks!
*February 28, 2008*

**Maths**

Thank you
*February 28, 2008*

**Maths**

Solve the problem. Assume that simple interest is being calculated. Round your answer to the nearest cent. Susie borrowed $7500. from a bank for 18 months with interest of 5% per year. Find the total amount she repaid on the due date of the loan. (Use: I=prt)
*February 28, 2008*

**chemistry**

If the molecular speed of a gas increases, its rate of diffusion will__________.
*February 27, 2008*

**Chem**

what's the answer?
*February 27, 2008*

**General Chemistry**

Vinegar is a 5.0% solution by weight of acetic acid in water. Given that the pH for vinegar is 2.41 and that Ka= 1.8E-5 and the density s 1.00g/mL, what is the percent dissociation of acetic acid in vinegar? I know the % dissociation equals the amount which did dissociate 5.0%...
*February 27, 2008*

**Physics**

It is probably easy, but i don't know where to start A hockey puck leaves a player's stick with a speed of 9.50 m/s and slides 27.0 m before coming to rest. Find the coefficient of friction between the puck and the ice. Thank You for helping me!!!
*February 25, 2008*

**physics**

the tension T=ma, since the only acceleration is that due to gravity.. a=g (9.8m/s^2) so T=0.442*9.8
*February 25, 2008*

**Science Proof-reader needed!**

The current research project involves examining the photoreceptors of the fruit fly, Drosophila Melanogaster. Over the last 6 weeks, I have been spending about 2 hours a week working with a program called ImageJ and various slices of photoreceptor cells of Drosphila. I have ...
*February 20, 2008*

**Proofread/Editing**

The current research project involves examining the photoreceptors of the fruit fly, Drosophila Melanogaster. Over the last 6 weeks, I have been spending about 2 hours a week working with a program called ImageJ and various slices of photoreceptor cells of Drosphila. I have ...
*February 20, 2008*

**Chemistry**

Could I plese have an example of a everday experience of a chemical process for which a rate increases with temperature? I thought of ice melting but its a physical change...
*February 19, 2008*

**College Calculus**

What is the integral of cos^6x? I tried half angle identities but it didn't really help...
*February 18, 2008*

**Chemistry**

Calculate ∆G (in kJ) at 541 K for the following reaction under the given conditions. Use data obtained from the table below and assume that ∆Hfo and So do not vary with temperature. Report your answer to three significant figures in scientific notation (i.e. 1.23E4...
*February 17, 2008*

**Psychology**

What are electrolytic lesions in terms of psychology and the brain? I can't find it anywhere and I dont know what it means...
*February 11, 2008*

**Bio-Genetics**

In watermelons the allele for green color and for short shape are dominant over the alleles for striped color and for long shape. A plant with long striped fruit is crossed with one heterozygous for both characteristics. The results are: green, short: 14 green, long: 96 ...
*February 9, 2008*

**Algebra 1**

Since it takes 25 minutes at 37.5 MPH, we know that in 60 minutes, they would go 37.5 miles. We need to know how long to commute is. 25/60 = 5/12, so you multiply 37.5 by 5/12. The answer is 15.625, this is how long the commute is. 15 MPH is 4 minutes per mile, so you multiply...
*February 7, 2008*

**Chemistry**

The total pressure in a flask containing air and ethanol at 25.7 C is 878 mm Hg. The pressure of the air in the flask at 25.7 C is 762 mm Hg. If the flask is immersed in a water bath at 45.0 C, the total pressure is 980 mm Hg. The vapor pressure of ethanol at the new ...
*February 4, 2008*

**chemistry**

A) If you make up a solution of 50 mL of 0.1 M TRIS in the acid form, what will be the pH? (pka of TRIS: 8.3, molecular wt: 121.1 g) B) if you add 2mL of 1 M NaOH to the solution, what will be the pH? Thank you.
*February 2, 2008*

**chemistry**

When Dr. Farrell was a graduate student, he once made up a pH 8.0 sodium acetate buffer. Why would the casual observer to this buffering faux pas come to the conclusion that he had the intellectual agility of a small soap dish?
*February 2, 2008*

**chem**

The total pressure in a flask containing air and ethanol at 257C is 845 mm Hg. If the pressure of the air in the flask is 762 mm Hg, the vapor pressure of ethanol is ? mm Hg.
*January 31, 2008*

**Physics**

well 1 W = J/s So, 19 kW is 19000 J/s. But you want to find time, so you want to have seconds in the denominator, you you would multiply the inverse of the watts times the amount of work. so (1 sec/19000 J) * (6.8 X 10^7 J) Joules should cancel out with joules and you should ...
*January 29, 2008*

**Lab Equipment**

alright sorry, I posted that before I saw your second answer but number 2 is crucible so I am all set.
*January 29, 2008*

**Lab Equipment**

thanks, I also found that number 1 wish wire gauze. Now I just need number 2
*January 29, 2008*

**Lab Equipment**

What is a square mesh with a fiber center used for support? 9 letters, ends with an E What is a porcelain container used to heat things? 8 letters, second letter is "R" What type of bottle is used for storing acids and bases? 7 letters, _E_G_ _T Help? Thanks!
*January 29, 2008*

**Algebra**

you cant do that, Miley, the m's and n's are separated by an addition sign, so you cant use the quotient of powers rule
*January 28, 2008*

**Algebra**

SImplify: (x - 9/x) / (1 + x/3) and (m^-1 + n^-1) / (m^-3 + n^-3) I have no idea what to do
*January 28, 2008*

**physics**

a pulley with rotational inertia of 1.5 times 10 ^-3 kg times m^2 about its axle and a radius of 15 cm is acted on by a force applied tangentially at its rim. The force magnitude varies in time as F=.5t + .3 t^2, where F is in newtons and t in seconds. The pulley is initiall ...
*January 28, 2008*

**Chemistry**

Hey, can you help me balance this equation? Cu2S + HNO3 --> Cu(NO3)2 + CuSO4 + NO2 +H2O Thanks!
*January 24, 2008*

**AP CHEM**

thanks
*January 24, 2008*

**AP CHEM**

what type of cubic structure is iron?
*January 24, 2008*

**Chemistry**

thanks, this is how i calculated it: 1 mol Fe/.141 mol/cm^3 = 7.10 cm^3 (the .141 came from converting the density in to moles) is that correct? then the next step in the problem is to find the volume of 1 mol of Fe atoms assuming each atom to be spherical. the atomic radius ...
*January 24, 2008*

**Chemistry**

The density of iron at 25 C is 7.871 g/cm^3 what is the volume of one mole of solid iron at 25 C? i understand that volume = m/d but how would i go about solving this?
*January 24, 2008*

**AP CHEM**

The density of iron at 25 C is 7.871 g/cm^3 what is the volume of one mole of solid iron at 25 C? i understand that volume = m/d but how would i go about solving this?
*January 23, 2008*

**CHEMISTRY**

how is liquid or the inital mass relevant to the question, if we're only concerned with the gas?
*January 20, 2008*

**CHEMISTRY**

A glass vessel has a mass of 53.8718 g when evacuated (no air). When filled with a liquid of density 1.319 g mL-1 it has a mass of 255.7390 g and when filled with an unknown gas at 752.3 torr and 16.12°C it has a mass of 54.2483 g. What is the molar mass of the gas, ...
*January 20, 2008*

**For DrBob222**

thank you so much for your help, i know it wasnt that difficult, i think i just confused myself with the temperatures. i get the answer now.
*January 19, 2008*

**For DrBob222**

i had to convert 38.3 to kelvin... because i converted the initial T to kelvin.
*January 19, 2008*

**For DrBob222**

the chemistry question: v=0.465L T=559.15K P=112.496 kPa Pv/t = Pv/t 112.kpa(0.465)/559.15 = (x)(0.464428)/(247.8) x= 49.9 kPa ...i skipped conversion steps, but i'm pretty sure i did those right..
*January 19, 2008*

**Chemistry**

A sample of Kr gas has a volume of 465 mL at 286°C and 844 torr. When the gas is cooled by 38.3°C, its volume is reduced by 0.572 mL. What is the final pressure of the gas in kPa? the answer is supposed to be 105 but i keep getting 49.9!!!!!!
*January 19, 2008*

**CHEMISTRY**

A 8.90-g sample of ethane, C2H6, is mixed with 18.8 atm of O2 (an excess) in a 1.50 L combustion chamber at 130.0°C. The combustion reaction to CO2 and H2O is initiated and the vessel is cooled back to 130.0°C. What is the final pressure in the combustion chamber ...
*January 17, 2008*

**science**

what is a mineral
*January 17, 2008*

**Chem Midterm Review**

Ok, so I've been really busy with midterms and my chemistry one is tomorrow. Now, I never intended to let so much time slip by before i started studying, but it happened. It's one of my most important exams. Do I still have a chance of passing? If so, how should I ...
*January 16, 2008*

**math**

a. y= 4x b. y= 2x c. y= 1 half x
*January 14, 2008*

**math**

identify the value of m in each equation. Then match each equation with it's graph.
*January 14, 2008*

**Calculus**

how did you get ry and r^2y for y' and y''?
*January 12, 2008*

**Calculus**

I posted this several days ago but it hasn't been answered and I still can't figure it out: For which values of r does the function defined by y=e^(rt) satisfy the differential equation y''+ y'-6y = 0
*January 12, 2008*

**Calculus**

For which values of r does the function defined by y=e^(rt) satisfy the differential equation y''+ y'-6y = 0
*January 10, 2008*

**Chemistry**

Yeah, I know that, but why can Copper lose either one or two while cadmium only has a +2 OS. I think the answer has something to do with valence electrons, but I'm not sure exactly.
*January 8, 2008*

**Chemistry**

Why can Copper have both a +1 and +2 oxidation state?
*January 8, 2008*

**Ap Chemistry**

In a class discussion, my teacher told me that 74.06% of the volume of each unit cell is occupied by atoms (in the cubic closest structure). Where does this percentage come from? How can I find it?
*January 7, 2008*

**Angles...**

How do i express angles in a radian measure as multiples of pi. For example, suppose i have an angle of 30 degrees, and a angle of -270 degrees. How would I express them in a radian measure as a multiple of pi?. Thanks.
*January 6, 2008*

**Chemistry**

Thank you
*January 1, 2008*

**Chemistry**

or CH2 double bond C(CH3)CH(CH3)CH3
*January 1, 2008*

**Chemistry**

would 1. be CH3C(CH3) Double bond C(CH3)CH3
*January 1, 2008*

**Chemistry**

Hey Everyone I was wondering how I could write the condensed structural formula for the following organic chemicals: 1. 2,3-dimethyl-2-butene 2. 4-ethyl-2-hexyne 3. 3,3,6-trimethylnonane 4. 3-ethyl-4-prophylheptane 5. 3-octanol 6. 2-methyl-2-pentene 7. 5-methyl-1-hexene 8. 2,2...
*January 1, 2008*

**Math**

List the first eight prime numbers.
*December 17, 2007*

**Writing**

I am looking for some written a one act play. Write anc act out a one act play in front of class covering a specific workplace issue , exapmple my include sexual harassment, workplace stress, great/bad bosses etc.
*December 10, 2007*

**physics**

The radiation curve of the sun shows that the brightest light fro the sun is yellow- green. Why, then, do we see the Sun as whitish instead of yellow green?
*December 8, 2007*

**physics**

then it has to be reading glasses.
*December 8, 2007*

**physics**

Suppose that sunlight falls both on a pair of reading glasses and on a pair of dark sunglasses. Which pair of glasses would you expect to become warmer?
*December 8, 2007*

**Chemistry**

Barium's Oxidation State is +2, Nitrate's Oxidation state is -1 Does that help?
*December 6, 2007*

**Physics**

What two ways can waves interact? ^I have no clue what its asking
*December 6, 2007*

**Is this how you derive the formula for arc length?**

in the third step, how did you integrate the right side with no delta-variable?
*December 4, 2007*

**chem**

A 1.00 L flask containing 450 torr of H2 is connected to and mixed with a second flask with a volume of 0.500 L containing 250 torr N2. What is the final pressure of the resulting mixed gas system? a) 250 torr b)383 torr c) 450 torr d) 575 torr e) it cannot be determined
*December 2, 2007*

**chem**

A 1.00 L flask containing 450 torr of H2 is connected to and mixed with a second flask with a volume of 0.500 L containing 250 torr N2. What is the final pressure of the resulting mixed gas system? a) 250 torr b)383 torr c) 450 torr d) 575 torr e) it cannot be determined
*December 2, 2007*

**chem**

Suppose that Quebec had managed to succeed from Canada and became an independent country. Just to be difficult, they decreed that they will only measure pressure in mm Hg and volume in cm3. What value for R, the ideal gas constant, would students in Quebec use when solving the...
*December 2, 2007*

**Math**

Prove that a simple graph with n >_ 2 vertices must have atleast two vertices with the same degree. There was a hint given in the book saying that the key to this is the graph can not have both a vertex of 0 degree and a vertex of n-1 degree
*December 1, 2007*

**Math**

It means that it is attached to that many other vertexes, say if a vertex is attached to two other vertex by lines then it has degree 2
*December 1, 2007*

**Math**

Prove that a simple graph with n >_ 2 vertices must have atleast two vertices with the same degree. There was a hint given in the book saying that the key to this is the graph can not have both a vertex of 0 degree and a vertex of n-1 degree Thanks
*December 1, 2007*