Monday

March 30, 2015

March 30, 2015

Total # Posts: 20,743

**Chemistry**

one C per molecule? 6.02 * 10^23 molecules per mol 2.46 * 10^25 molecules *(1/6.02*10^23) = 40.9 mols How many grams? 40.9 * (12 + 4(35.5) ) what volume? grams / 2.71 g/mL
*March 29, 2015*

**Differential Calculus**

radius of circle = r side of square = s 10 = 4 s + 2 pi r so s = 2.5 - .5 pi r A = pi r^2 + s^2 or A = pi r^2 + 6.25 - 2.5 pi r + .25 pi^2 r^2 A = (.25 pi +1)pi r^2 -2.5 pi r + 6.25 I am going to use calculus, you can complete the square to find vertex of parabola dA/dr = 0 ...
*March 29, 2015*

**Geometry**

I used 400, use 500
*March 29, 2015*

**Geometry**

2 h + 2 w = 400 h + w = 200 w + 40 + w = 200 2 w = 160 w = 80 h = 120
*March 29, 2015*

**Civics to Ms.Sue**

Ms Sue is completely correct. There were presidents under the Articles.
*March 27, 2015*

**Civics to Ms.Sue**

It did not allow for a Department of Commerce :)
*March 27, 2015*

**Civics to Ms.Sue**

Well, the Articles of Confederation allowed for a president.
*March 27, 2015*

**Algebra 1**

0 = -0.04x^2+1.3x+56 or 0 = 0.04x^2 - 1.3x - 56 solve quadratic
*March 27, 2015*

**us history**

Now why would a state stay in the Union even if some of its residents had slaves? Maybe some of them did not have slaves and disagreed with the others?
*March 27, 2015*

**us history**

I do not think it is b or d
*March 27, 2015*

**Algebra 1**

.04 x^2 - 8.3 x - 4.3 = 0 http://www.webgraphing.com/quadraticequation_quadraticformula.jsp#
*March 27, 2015*

**Algebra 1**

y = x (-.04 x + 8.3) when is y = 0 at the start of course but also when .04 x = 8.3 or x = 207.5 meters I think you left a significant figure out :)
*March 27, 2015*

**Algebra**

y = k/x 300 = k /4 so k = 1200 y = 1200/150 y = 8
*March 27, 2015*

**Algebra**

I bet you mean [ f(x) - f(a) ] / (x-a) Parentheses are VITAL ! f(a) = -2 a^2 + 5 a - 1 so [ -2(x^2-a^2) +5(x-a) -1+1 ]/(x-a) = [-2(x-a)(x+a) + 5(x-a) ]/(x-a) = -2(x+a)+5 Note for future calculus purposes that the limit of this as a approaches a this becomes -4 x + 5
*March 27, 2015*

**us history**

I do physics actually. I just happened to know this.
*March 27, 2015*

**us history**

Jim Crow laws, C is right.
*March 27, 2015*

**Algebra**

distance = pi D in feet = pi * 64 * (1 mile/5280 ft) time = 25 s (1 h /3600 s) divide the distance in miles by the time in hours
*March 27, 2015*

**algebra**

y dy = x dx y^2/2 = x^2/2 + c or y^2 = x^2 + c (-3)^2 = 0 + c so c = 9 y^2 = x^2 + 9 y = +/- (x^2+9)^(1/2) since only y = -3 is given I think your answer correct
*March 27, 2015*

**math**

AB^2 = 64 + 4 = 68 BC^2 = 9 + 9 = 18 AC^2 = 25 + 25 = 50 Note that 68 = 50 + 18 therefore a right triangle
*March 27, 2015*

**physics**

F = m A F = (10.45)(2.5)
*March 27, 2015*

**Economics**

10 years 10.3 = 1.9 (1+r)^10 10 log(1+r) = log(5.42) log(1+r) = .0734 1+r = 1.184 so 18.4 percent per year
*March 27, 2015*

**math**

http://davidmlane.com/hyperstat/z_table.html
*March 27, 2015*

**Pre-Calculus**

Because she used parentheses.
*March 26, 2015*

**Math**

a) .15 * 15 = 2.25 NOT 1 c) correct e) corrtect
*March 26, 2015*

**Math**

b) CORRECT c) .045 * 1000 = 45 CORRECT ! d) NO way, you really feel 45 m is almost half a kilometer? e) 4500 / 1000 = 4.5 meters!
*March 26, 2015*

**Math**

old area = 400 ft^2 perimeter = 20+80 = 100 so 4 s = 100 s = 25 s^2 = area = 625 625 - 400 = ???
*March 26, 2015*

**Math**

4 = 1 + 3 or 2 + 2 or 3 + 1 so 3 out of 36 which is 1/12
*March 26, 2015*

**Geometry**

L w = 2 2 L * 3 w = 6*2 = 12
*March 26, 2015*

**mathematical physics**

we need the component of force in the direction of motion. F dot vector tangent to motion tangent to motion is velocity vector dX = Vdt if X is position vector and V is velocity vector X = t i + t j + t k V = dX/dt = i + j + k F dot V = y^2z^3 + 2 xyz^3 + 3x y^2 z^2 = t^5 + 2 ...
*March 23, 2015*

**math**

Thank you Reiny. Indeed we had quite a time getting ready for the first day of sailing practice.
*March 23, 2015*

**math - binomial dist, no time to do it**

use binomial distribution. I have to go clean seagull poop and snow off high school sailing floats, will check back this afternoon to see if you got it.
*March 23, 2015*

**Algebra 1**

y = x straight line through origin slope of one. y = 1 x + 0
*March 22, 2015*

**CHEMISTRY**

P V = n R T V same n same R same T same so partial pressure of each is 1/2 atm.
*March 22, 2015*

**Algebra**

http://www.jiskha.com/display.cgi?id=1427052839
*March 22, 2015*

**Algebra**

No problem :)
*March 22, 2015*

**Algebra**

I wrote (3 y - ) (y + ) and tried factors soon saw needed (3 y + ) (y - ) then fooled with 3 and 4 and then 6 and 2 until it worked
*March 22, 2015*

**Algebra**

Sure, fooled around with factors of 12 3 and 4 did not work, 1 and 12 did not work, so tried 6 and 2
*March 22, 2015*

**Algebra**

You are welcome.
*March 22, 2015*

**Algebra**

(3 y + 2)(y - 6)
*March 22, 2015*

**math**

combinations of 15 ten at a time n = 15 r = 10 C(n,r) = n!/[ r!(n-r)! ] = 15! /[ 10! (5!) ] = 15*14*13*12*11 /(5*4*3*2) = 15/15 * 14/2 * 13 * 12/4 * 11 = 7 * 13 * 3 * 11 = 3003
*March 22, 2015*

**algebra**

6 by 6 matrix of possibilities but 5 and 1 is the same as 1 and 5 for example so really not 36 possible results but only the diagonal and those below (or those above) so 6 + 5 + 4 + 3 + 2 + 1 = 21 possible combinations of which 3 add to 6 (they are (3,3)(2,4)(5,1) ) so THREE ...
*March 22, 2015*

**College Math**

new length = 36 - 2x new width = 24 - 2 x so V = (36-2x)(24-2x)x = 864x - 120 x^2 + 4 x^3 I am glad you do derivatives because I do not feel like finding the vertex. dV/dx = 864 -240 x + 12 x^2 0 = 72 - 20 x + x^2 x = [ 20 +/- sqrt(400 -288) ]/2 = [ 20 +/- 10.6 ] /2 = 15.3 or ...
*March 20, 2015*

**physics**

I can not because I do not know how far south the cat walked
*March 17, 2015*

**physics**

mg = 17*9.81 = 167 N weight 70 = mu (167) mu = 70/167 static 53 = mu (167) mu = 53/167 kinetic
*March 17, 2015*

**Algebra**

2 x^2 - 2 x - 2 = -y x^2 - x -1 = -(y/2) x^2 - x = -y/2 + 1 x^2 - x + 1/4 = -y/2 + 1 + 1/4 (x- 1/2)^2 = -(1/2) (y - 5/2) vertex at ( 1/2 , 5/2 ) if x = 6 y = - 2(36) + 12 + 2 = -58 =================== check (5.5)^2 =? -1/2 (-60.5) ??? 30.25 = 30.25 sure enough :)
*March 17, 2015*

**math**

2*60 + 2 w = 200 w + 60 = 100 w = 40
*March 17, 2015*

**Math**

1 % is .01 .02/5 is clearly less than .01 (it is .004) .2/5 is like .4/10 too big 2/5 even bigger 2/50 like 4/100 like .2/5 too big 2/500 is 4/1000 which is small enough (.004 again)
*March 17, 2015*

**math**

3/5 * 1/3 * x = 8 x = 8 * 15 / 3 x = 40 ================ check: 2/5 * 40 = 16 spent, 24 left 2/3 * 24 = 16 spent, 8 left --- sure enough
*March 17, 2015*

**Vectors**

vector QP = 3 i + 8 j + 2 k vector QR = 1 i + 6 j - 2 k cross product i j k 3 8 2 1 6 -2 -28 i + 8 j + 10 k or -14 i + 4 j + 5 k so for plane -14 x + 4 y + 5 z = d try (1,5,6) to get d -14 +20 + 30 = d d = 36 check with (-1,3,2) 14 + 12 + 10 = 36 sure enough we are on a roll ...
*March 17, 2015*

**physics**

(1/2) M V^2 = (1/2) K X^2 1330 v^2 = 4.12*10^6 (.0499)^2
*March 17, 2015*

**Science Help Please**

Your answer to umber 7 is likely to upset any physicist. Please read the chapter in your text. Go back to the chapters on waves on strings and in trumpets. short wave --> high frerquency
*March 13, 2015*

**Science Help Please**

2 A 5 D 6 A 7 D Oh dear :( 13 C
*March 13, 2015*

**physics**

Huh? 500 Joules is 500 Joules.
*March 13, 2015*

**PHYSICS**

20 meters down pressure = rho g h = 1000kg/m^3*9.81*20 = 196,200 = 1.96 *10^5 Pascals I guess the radius is .4 m??? A = pi(.4)^2 F = P*A = 98,621 Newtons
*March 13, 2015*

**vectors and geometry**

2*5 + 3*-2 + 4*1 10 - 6 + 4 8
*March 13, 2015*

**vectors and geometry**

a+b = 6 i -1 j + 0 k trick question or typo cross product = |A||A| sin theta theta = 0 so cross product = 0
*March 13, 2015*

**Check Answers (Math)**

at x = 0, B is below at all other points, B is below so yes, right, B is wider.
*March 10, 2015*

**physics**

-19+6 = -13 so 1.6 * 10^-13 uC /electron so (1/1.6)*10^13 electrons/uC = .625 * 10^13 = 6.25 * 10^12 electrons
*March 10, 2015*

**physics**

assume light travels at very very high speed so you see the lightning immediately. Then distance = speed of sound * time distance in km = (1/3) t so speed of sound must be about 1/3 km/sec or about 333 m/s 8/3 km
*March 10, 2015*

**MATH**

right triangle, hypotenuse = 5.4 so sin I = JH/5.4 so JH = 5.4 sin 64
*March 10, 2015*

**physics**

G M/r^2 = .39 G M/Re^2 r^2 = Re^2/.39
*March 9, 2015*

**physics**

horizontal component of g = v^2/r g sin theta = v^2/r here g = 32 ft/s^2 v = 56 mi/h * 5280 ft/mi * 1 h/3600 s r = 1000 ft
*March 9, 2015*

**maths(direction cosines of vectors)**

change in x = 7 - 4 = 3 change in y = 6 - 2 = 4 change i z = 14 - 2 = 12 so V = 3 i + 4 j + 12 k is in the direction magnitude: sqrt (9+16+144) = 13 dot product with unit x vector for example V dot 1 i = 13 * 1 * cos angle so cos angle = 3/13 then y axis cos angle = 4/13 and x...
*March 9, 2015*

**Calculus 1**

2 x dx + 2 y dy = 2 (2 x^2+4 y^2 -x)(4 x dx + 8 y dy -dx) at (0, 1/4) 0 +(1/2)dy = 2(0+4(1/16)-0)(8(1/4)dy -dx) (1/2) dy = 2 (1/4)(2 dy-dx) = dy - (1/2) dx dy = 2 dy - dx dy = dx dy/dx = slope = 1 so y = x + b put in your point to find b
*March 9, 2015*

**Calculus (Integral)**

well, you could try this: http://www.wolframalpha.com/input/?i=integral&a=*C.integral-_*Calculator.dflt-&f2=25+%2F%28+e^x%2825+%2B+e^2x%29+%29+&f=Integral.integrand_25+%2F%28+e^x%2825+%2B+e^2x%29+%29+&a=*FVarOpt.1-_**-.***Integral.rangestart-.*Integral.rangeend--.**Integral....
*March 9, 2015*

**math**

I assume you mean: Factor 21 a^2 - 19 a - 22 well, we need -33 + 14 = -19 (7 a - 11)(3 a + 2)
*March 8, 2015*

**math**

2D * 3 D = 6 D^2 = 6 (2R)^2 = 24 R^2
*March 8, 2015*

**5th grade Science**

the density of water is about 1 g/cm^3 This boat is more dense than water, it is in fact more like a rock than most plastic and is certainly not hollow. the upward force on an object in water is the weight of water displaced by the volume of the object in the water. If the ...
*March 8, 2015*

**Social studies**

http://www.u-s-history.com/pages/h127.html
*March 8, 2015*

**geography**

Oh, the s makes it hard http://eos.ucs.uri.edu/EOSWebOPAC/OPAC/Details/Record.aspx?TaskCode=61612&BibCode=EOSMAIN|5127150|1|288252&HitCount=1&SelectionType=1&SearchType=2&CurrentPage=1&IndexCode=-1&SortDirection=Descending
*March 8, 2015*

**geography**

My students worked on one: https://eos.ucs.uri.edu/EOSWebOPAC/OPAC/Details/Record.aspx?TaskCode=61612&BibCode=EOSMAIN|5127150|1|288252&HitCount=1&SelectionType=1&SearchType=2&CurrentPage=1&IndexCode=-1&SortDirection=Descending
*March 8, 2015*

**Physics**

at (0,0) the fields from the first two charges cancel each other. to get a field at (0,0) in the y direction the x components of charges Q must cancel. Therefore one must be +Q and the other -Q If the field is up (+ i direction) the one below the axis is +Q and the one above ...
*March 8, 2015*

**so what did you get ?**

I already did this stuff in school. It is your turn to try. I suspect someone will check your results.
*March 8, 2015*

**Math Functions**

p = R - C = 5 x^2 + 19 x - 10 where is that zero? solve quadratic x = [ -19 +/- sqrt (361+200) ]/10 = [ -19 +/- 23.7 ]/10 = .469 thousand = 469
*March 8, 2015*

**Physics**

initial speed up Vi = 21 sin 37 v = Vi - 9.81 t at top v = 0 so t = ( 21 sin 37 ) / 9.81 = time rising time falling = time rising so 2 t = time in air
*March 8, 2015*

**math**

If only integer sides 1 , 10 , 1 nope sum of two must be > third 5 , 4 , 3 sure one 4 , 4 , 4 sure two 3, 3, 6 , nope, straight line 2 , 5 , 5 sure three 2 , 4 , 6 nope you found a fourth ?
*March 8, 2015*

**math**

do they have integer lengths? if so 2,5,5 4,4,4 5,4,3
*March 8, 2015*

**math**

Google Heron's formula Area^2 = A^2 = S(S-a)(S-b)(s-c) where S = (1/2) perimeter = 6 here so A^2 = 6 (6-a)(6-b)(6-c) so look for maximum of (6-a)(6-b)(6-c)
*March 8, 2015*

**physics**

It slows down, shorter wavelength, same frequency (note it can not change frequency. There is no storage of waves, the same number have to pass a given point per unit time on each side.) lambda = V * T so lambda = V/f if V goes down/ lambda goes down
*March 8, 2015*

**College Math**

e^rt = e^(.062*7) = 1.543418868 times $ 2600 = $ 4012.89
*March 8, 2015*

**Maths**

if you mean in radians 55 deg * (pi rad/180 deg) .9599 radians
*March 8, 2015*

**physics**

Every turn you go one circumference, 2 pi R
*March 8, 2015*

**physics**

must know radius R C = 2 pi R so 500 * 2 pi R
*March 8, 2015*

**Algebra 2**

if so then 5 -2.5 sqrt 3 + 2.5 i -2.5 sqrt 3 - 2.5 i
*March 8, 2015*

**Algebra 2**

x^3 = 125 x = 5 works you do not say if you also do complex numbers
*March 8, 2015*

**physics**

40 * 5 60 * 5 * 0.40 Joules
*March 7, 2015*

**physics**

force down = m g = 63*9.81 N mass accelerated = 63+10 = 73 kg a = F/m = 9.81 (63/73) m/s^2
*March 6, 2015*

**Social Studies**

Although the astrolabe has origins traced back over 1,500 years, it was highly developed in the Islamic world by 800 and was introduced to Europe from Islamic Spain (Andalusia) in the early 12th century. It was the most popular astronomical instrument until about 1650, when it...
*March 6, 2015*

**linear programming - suspect not correct problem statement**

x = paper y = cans p = 500 x + 350 y y </= 200 x </= 200 x >/= 10 y >/= 80 I do not understand last constraint, redundant if y</=200 rectangle corners at (10, 80) (10,200) (200, 80) (200,200) well, go ahead and evaluate p at each corner but obviously mas at (...
*March 6, 2015*

**algebra**

6, 12, 18, 24 is 4 4/24 = 1/6 1 - 1/6 = 5/6 permutations of 12 things 4 at a time is n!/(n-r)! = 12!/8! = 12 * 11 * 10 * 9 = 11,880 if it is a number I would call it quatitative.
*March 6, 2015*

**Math**

B 5 to 15 is one to three not one to five C 3/5 = painting/sculpture so 3/8 = painting/total 5/8 = sculpture/total 3/8 * 24 = 9 5/8 * 24 = 15
*March 3, 2015*

**maths**

45 = 5*3*3 60 = 5*3 *2*2 so we need 5*3*3*2*2 = 180
*February 28, 2015*

**Physics**

North: 4 + 1.2 sin 35 East 1.2 cos 35 + 1.3
*February 28, 2015*

**Math**

That seems to work.
*February 28, 2015*

**Physics**

Vi = 26.5 sin 30.9 = 13.6 v = Vi - g t at top v = 0 9.81 t = 13.6 at top t = 1.39 seconds up u = 26.5 cos 30.9 u = 22.7 d = u t = 22.7*1.39 = 31.6 meters
*February 28, 2015*

**Physics**

Weight does not matter. v = sqrt (2 g h)
*February 27, 2015*

**statistics**

http://davidmlane.com/hyperstat/z_table.html
*February 27, 2015*

**Vocabulary**

We could calculate it all right. It was so lethargic it was frigid.
*February 27, 2015*

**Chemistry Need Help**

You only have 1.50 mol of Cl2 so you are only going to get 3.00 mol of ClF You have 0.25 mol of excess F2 left over.
*February 27, 2015*

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