Wednesday

July 29, 2015

July 29, 2015

Total # Posts: 21,560

**stastic**

Given the following information about a sample, calculate a z score for a test grade of 91. = 87, s = 4.01 (Points
*April 2, 2015*

**Algebra 2**

http://www.easycalculation.com/statistics/standard-deviation.php
*March 31, 2015*

**Algebra 2**

https://www.easycalculation.com/statistics/standard-deviation.php add up the squares of the difference between each value and the mean divide it by 7 or 6 depending on if the population sd or just sd is desired take the square root.
*March 31, 2015*

**physics**

1 hp = 550 ft lbs/s so 25 hp = 13,750 ft lbs/s = Torque *radians/sec 1800 rev/m (2 pi rad/rev)(1 m/60 s) = 188 radians/s so Torque = 13750/188 = 72.9 ft lbs
*March 31, 2015*

**science help.. pls help me dr.bob22 or damon**

In one case it is ionic In the other case it is covalent However In both cases it is chemical
*March 31, 2015*

**science help.. pls help me dr.bob22 or damon**

Water is a covalent bond but a special polarized one called a "hydrogen bond" that results in attraction between water molecules
*March 31, 2015*

**Algebra 2**

If c is the hypotenuse (opposite the right angle) then c^2 = a^2 + b^2 or b^2 = 361 - 9 b = sqrt(352) = 18.8 sin A = a/c sin B = b/c
*March 31, 2015*

**science help.. pls help me dr.bob22 or damon**

I think so.
*March 31, 2015*

**science help.. pls help me dr.bob22 or damon**

I suspect that finding that electrons surround a nucleus would be fatal for the hypothesis of indivisibility :)
*March 31, 2015*

**math - linear equation**

y = x y = -x
*March 31, 2015*

**science help.. pls help me dr.bob22**

been there done that below metals and halogens are likely to form ionic bonds
*March 31, 2015*

**pls help me dr.bob22 science**

Yes Oscar it is B. but you mean Zn + 2HCl = H2 + ZnCl2
*March 31, 2015*

**pls help me dr.bob22 science**

Yes
*March 31, 2015*

**pls help me dr.bob22 science**

If it is an ionic bond it is an ion K+ will do as will F- Cl2 is a complete molecule Ne is a noble gas which is too proud to react much.
*March 31, 2015*

**science help check**

Metals from Group 1 are most likely to form ionic bonds Halogens, group 17, are also likely to form ionic bonds
*March 31, 2015*

**Calculus - all the same question**

If you can follow the one I did, you can do the rest.
*March 30, 2015*

**Calculus**

dC/dx = 100 - .2 x at x = 35 dC/dx = 100 - 7 = 93 dollars per club at a level of 35 clubs by the way total C for 35 clubs = 3877.5 or about an average of 111 dollars per club
*March 30, 2015*

**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*