Friday

March 27, 2015

March 27, 2015

Total # Posts: 1,579

**math**

Formula for getting an interior angle of a regular polygon with n sides: I = 180(n-2)/n Substituting, I = 180(18-2)/18 I = 160 degrees Hope this helps~ :3
*September 24, 2013*

**Calculus**

Your answer is actually correct. :) d/dx (6/ln(x)) d/dx (6*(ln(x))^(-1)) = 6(-1)(1/x)(ln(x))^2 = -6/(x*(ln(x))^2)
*September 24, 2013*

**chemistry**

First, we have to get the molar mass of aniline. Just get a periodic table and add the individual masses of the elements in the chemical formula: C6H5NH2: 6*12 + 5*1 + 1*14 + 2*1 = 93 g/mol Then we get the mass of aniline using the given density and volume. Recall that density...
*September 23, 2013*

**Chemistry**

Nope, you can't directly convert the 1.27 g sample to moles of Mg because it is impure or not 100% Mg. Since there is some HCl left after the reaction, the impure Mg is the limiting reactant and HCl is in excess. Note that the Mg used was impure. To get the number of moles...
*September 22, 2013*

**Math**

#1. Not necessarily. For example, a = -5 and b = -3 |a| = 5 |b| = 3 |a| is greater than |b|, but -5 is NOT greater than -3. #2. Opposites are numbers which have the same distance (numerical value) from zero but different in directions (opposite signs). An example would be -5 ...
*September 22, 2013*

**Calculus**

lim (x^4-5x^3+7x^2-6x+3)/(x-1) as x->1 Note that if we substitute 1 to the function, the denominator becomes zero (and we don't want that). But take note that the numerator can be factored: lim (x-1)(x^3 - 4x^2 + 3x - 3) / (x-1) Thus the x-1 will be cancelled, and we&#...
*September 22, 2013*

**math**

If that's already the question, then yes. :3
*September 22, 2013*

**8th G-Math**

This means that the number of students did not exactly fill the total capacity of the 7 buses, because there are 6 who had to travel in cars. What we'll do here is first, we subtract the 6 "extra" students from the 405, so that we'll know the exact, total ...
*September 22, 2013*

**Math**

Represent the unknown with variable. Let x = time that Steve's brother travelled Recall that distance is equal to speed multiplied by time. We get their distances travelled and equate them (since it's said that they followed the same route and they'll overtake at ...
*September 22, 2013*

**maths**

Note that you can factor out a(a+b) from the two terms: a(a+b) * (a+b - 2b) Thus, a(a+b)(a-b) Hope this helps~ :3
*September 22, 2013*

**Algebra Answer Check**

Yup, they are all correct. :)
*September 21, 2013*

**Chemistry stoch1**

First we write the balanced chemical reaction involved: 3Fe + 4H2O -> Fe3O4 + 4H2 Since we have 18 g of steam, we have to convert this to moles and use the stoich ratios from the reaction to get amount of Fe needed to react with it. To convert mass to moles, we get the ...
*September 21, 2013*

**a**

0 > x^2 + 5x - 2 We can also rewrite this as x^2 + 5x - 2 < 0 First thing to do is find the roots of the equation. Since the quadratic equation is not factorable in just one look, we use the quadratic formula: x = ( -b +/- sqrt(b^2 - 4ac) ) / 2a Therefore, x = ( -5 +/- ...
*September 21, 2013*

**Math**

Note that when two lines are parallel, their slopes are equal. The given equation is 4x - 5y = 8. To get its slope, we change it to the form y = mx + b where m is the slope and b is the y-intercept. Therefore, 4x - 5y = 8 -5y = -4x + 8 y = (4/5)x - 8/5 The slope is equal to 4/...
*September 20, 2013*

**Geometry**

Note that we can form a right triangle here, with base equal to 100 ft and angle between hypotenuse and base equal to 48°. Let h = height of triangle, which is also equal to total height of statue minus the 5 ft elevation of the device. Thus, tan 48° = h / 100 h = 100...
*September 20, 2013*

**Geometry**

To get the distance, use the distance formula: d = sqrt((x2 - x1)^2 + (y2 - y1)^2) Assuming the point where the home lies is at the origin (0,0), thus the beach lies at (120, -30). Substituting, d = sqrt((120 - 0)^2 + (-30 - 0)^2) d = sqrt(14400 + 900) d = sqrt(15300) d = 123....
*September 20, 2013*

**Geometry**

Angle of depression is the angle below the horizontal that an observer must look in order to see an object below him. If you draw the figure, you can actually see that the hot-air balloon is located 25° above the horizontal. We actually formed a triangle here, with height ...
*September 20, 2013*

**Geometry**

It's easier if you drew the figure, but it's hard to draw figures here so I'll just describe it. :3 Note that the woman is 15 ft from the statue, and she looks up at an angle of 60° in order to see the top of statue. From here we can actually form a right ...
*September 20, 2013*

**MATH**

Let x = the stones that Eunice must take from Esther in the third round in order to be declared winner At start, Eu: 20 Es: 20 After first round, Eu: 20 + 5 = 25 Es: 20 - 5 = 15 After second round, Eu: 25 - 3 = 22 Es: 15 + 3 = 18 After third round, Eu: 22 + x = 30 Therefore, x...
*September 20, 2013*

**geometry**

I think we need to see the figure, but looking at the given, I think the point FG bisects and intersects BT at point O. Therefore we can say the lengths of segments BO and OT are equal, or 7x - 6 = 5x + 10 7x - 5x = 10 + 6 2x = 16 x = 8 Susbtituting, BO = 7x - 6 BO = 7(8) - 6 ...
*September 19, 2013*

**MATH**

Mira: 20 Noreen: 20 Olivia: 20 After they give pretzels, M: 20 - p N: 20 + p + q O: 20 - q What we can do here is add all of them and equate them to the sum of the ratio multiplied by a certain factor, say x: (20 - p) + (20 + p + q) + (20 - q) = (5+9+6)x The p's and q'...
*September 17, 2013*

**calculus**

y = (5e^x)/(cos x) Since 1/cos(x) = sec(x), we can also rewrite this as (5e^x)(sec(x)) Since two terms which are both functions of x are multiplied, we use the chain rule. Thus it becomes: (5e^x)(sec(x)) + (5e^x)(tan(x) * sec(x)) Simplifying, dy/dx = (5e^x)(sec(x))(1 + tan(x...
*September 17, 2013*

**calculus**

y = (sin x)^-1 This can also be rewritten as y = 1/(sin x) y = csc x Therefore, dy/dx = -cot(x) * csc(x) Hope this helps~ :3
*September 17, 2013*

**pre calcalus**

(x+4)^(2/3) = 9 To do this, we raise both side by 3/2, so that the exponent 2/3 of the term on the left side will be cancelled: (x + 4)^(2/3 * 3/2) = 9^(3/2) (x + 4)^(1) = 3^3 x + 4 = 27 x = 27 - 4 x = 23 To check, substitute the x value to the original equation: (23 + 4)^(2/3...
*September 16, 2013*

**math**

(4x)^(2/3) = (30x+4)^(1/3) To do this, note that it's much easier to work with whole number exponents. This we raise both side terms by 3, so that the denominator 3 will be cancelled: (4x)^(2/3 * 3) = (30x+4)^(1/3 * 3) (4x)^2 = (30x+4)^1 16x^2 = 30x + 4 Solving for x, 8x^2...
*September 16, 2013*

**AP Calculus**

f(x) = | (x)(x-3) / (9 - x^2) | (a) Domain & Zeroes of f? Domain is the set of all possible values of x. In the given function, note that the denominator can not be equal to zero, because any number divided by zero results to indeterminate (if 0/0) or infinity (if any non-zero...
*September 16, 2013*

**Physics**

R = a*t, or a = R/t Units of R = m^3 / s Units of t = s Thus, a = (m^3 / s) / s a = m^3 / s^2
*September 16, 2013*

**Math :(**

2b = b + 2 + b 2b = 2b + 2 We can see here that the 2b will be cancelled from both sides, and we're left with, 0 = 2 which is not possible. Thus there is no solution. Hope this helps~ :3
*September 16, 2013*

**math**

Recall that the perimeter of a square is equal to P = 4*s where s = length of one side Therefore, 80 = 4*s s = 80/4 s = 20 meters We need to find the area. Recall that the area of a square is just A = s^2 Substituting, A = 20^2 A = 400 m^2 Hope this helps~ :3
*September 16, 2013*

**Algebra Homework**

First we find the slope of the given points: m = (y2 - y1)/(x2 - x1) Substituting, m = (0 - (-2))/(-5 - k) m = 2/(-5 - k) Then, we get the slope of the given line. y = (5/9)x − 2 Note that it follows the form y = mx + b, where m is the slope and b is the y-intercept. ...
*September 16, 2013*

**Math**

2(4m + 6) = 8m + 6 8m + 12 = 8m + 6 Note that from here, we can see that there is no solution. The 8m will be cancelled from both sides, and we are left with 12 = 6 which is impossible. Thus, there is no solution, or there is no value of m that can satisfy the equation. Hope ...
*September 16, 2013*

**math**

If you mean √(2x - 7) + 8 = 11 Then, first we isolate the whole squareroot term on one side of equation: √(2x - 7) = 11 - 8 √(2x - 7) = 3 Then we square both sides: 2x - 7 = 9 2x = 9 + 7 2x = 16 x = 8 Note that if we're dealing with squareroots, we always...
*September 16, 2013*

**algebra**

What do you want to solve specifically? If you want to solve for x, V = 4/3 πx^3 4/3 πx^3 = V x^3 = V(3/(4π)) x = cuberoot( 3V/(4π))
*September 16, 2013*

**algebra**

I'm not sure if this is the same with the other post, but I'll just paste it here. If you mean √(2x - 7) + 8 = 11 Then, first we isolate the whole squareroot term on one side of equation: √(2x - 7) = 11 - 8 √(2x - 7) = 3 Then we square both sides: 2x...
*September 16, 2013*

**Math simplifying mixed radicals**

To do this, you have to factor the radicand (or the number inside the radical sign) and look for perfect squares. For instance, 2 * √(48) 2 * √(16*3) 2 * √(4*4*3) Express the repeating factors using exponents, so it's easier to see. Since four is ...
*September 14, 2013*

**Math simplifying mixed radicals**

To do this, you have to factor the radicand (or the number inside the radical sign) and look for perfect squares. For instance, 2 * √(48) 2 * √(16*3) 2 * √(4*4*3) Express the repeating factors using exponents, so it's easier to see. Since four is ...
*September 14, 2013*

**Math simplifying mixed radicals**

Hi! Just to clarify, are those numbers on the left (the 2, 3, 6, 3, etc.) are multiplied with the squareroot terms or are written as small number which is therefore part of the radical sign?
*September 14, 2013*

**Math**

Represent the unknowns with variables. Let x = total amount of Muffins sold in dollars Let (4 1/2)x = total amount of Doughnuts sold in dollars (according to the first statement) Then we set up the equation. Since their total is $44,000: x + (4 1/2)x = 44000 Then we solve for ...
*September 14, 2013*

**chemistry**

First, we write the balanced chemical equation involved. Since the reaction is synthesis of NH3, N2 + 3 H2 -> 2 NH3 Since N2 is excess, H2 is limiting and we therefore use its moles to determine the amount of NH3 produced. In the equation, there are 2 moles of NH3 produced ...
*September 14, 2013*

**math**

Domain of what? If the required is their individual domains: 1. For f(x) = 1/(x^2 - 8x - 9) Note that domain is the set of all possible values of x. In the function, note that the denominator must not be equal to zero because 1/0 is infinity. Therefore, we find the values of x...
*September 14, 2013*

**math**

What is required to find? :3
*September 14, 2013*

**Radius Question Geometry(college level)**

I'm not sure if there is a given figure for this problem, but if the three separate circles are tangent with the other with their centers aligned (or can be connected by a straight line), then yes, you get 60 cm for the diameter of the new, bigger circle which ...
*September 14, 2013*

**calculus**

lim (x^2 + 6x + 5)/(x^2 - 3x - 4) as x-> -1 Not that we can factor both numerator & denominator, lim (x+5)(x+1) / (x-4)(x+1) We can thus cancel the x+1, leaving lim (x + 5)/(x - 4) as x-> -1 Substituting x = -1, = (-1 + 5) / (-1 - 4) = 4 / -5 = -4/5 Hope this helps~ :3
*September 14, 2013*

**Math**

Recall the point-slope form of an equation: y - y1 = m(x - x1) where m = slope (x1, y1) = point on the line Substituting, y - 6 = -8(x - 4) y - 6 = -8x + 32 y = -8x + 38 (slope-intercept form), or 8x + y = 38 (standard form), or 8x + y - 38 = 0 (general form) Hope this helps~ :3
*September 13, 2013*

**MATH**

Recall the formula for slope of a line: m = (y2 - y1) / (x2 - x1) where (x1, y1) and (x2, y2) are the points on the line Substituting, m = (4 - 2) / (3 - (-1)) m = 2 / (3+1) m = 2/4 m = 1/2 Hope this helps~ :3
*September 13, 2013*

**Math**

Recall the formula for slope of a line: m = (y2 - y1) / (x2 - x1) where (x1, y1) and (x2, y2) are the points on the line Substituting, m = (9 - 5) / (4 - 3) m = 4/1 m = 4 Hope this helps~ :3
*September 13, 2013*

**Maths**

Hmm not sure if this can be accepted: 4 + (4-4)/4 ..but at least it has four 4's. XD
*September 13, 2013*

**Maths**

9*9+9+9+(9/9) ...six 9's. XD I'm not sure how if only four 9's should be used with normal math operations. Hmm...
*September 13, 2013*

**Maths**

9+9+(9+9)/9 lol there are five 9's. XD I'm not really sure how if there are only four 9's. :3
*September 13, 2013*

**Math**

If you mean that the a regular 40-sided polygon, recall that the formula for total number of diagonals of a polygon with n sides is, D = n(n-3)/2 Therefore, D = 40(40-3)/2 D = 740 diagonals Hope this helps~ :3
*September 13, 2013*

**Math - Factoring**

I think you forgot to type the choices. But anyway, you just have to apply some exponential rules and division rules: *When 2 is raised with an integer (greater than 1), the last digit of the number has a repeating pattern of 2, 4, 8, 6. *A number is divisible by 10 if the ...
*September 13, 2013*

**Math - Polygons**

Recall that the formula to find the measure of one interior angle of a polygon with n sides is, I = 180(n-2)/n Substituting, 150 = 180(n-2)/n 150n = 180n - 360 -30n = -360 n = 12 sides Hope this helps~ :3
*September 10, 2013*

**mathssssSsssss**

#1. Note that if you draw a broken line corresponding to the height of the parallelogram, you would form a right triangle in which the hypotenuse is 10 cm and one of the angles is 55 degrees. We can actually solve for the height, which is equal to 10 * sin (55) = 8.19 cm A of ...
*September 10, 2013*

**Math - Quadrilaterals**

Note that the sum of interior angles of a quadrilateral is equal to 360 degrees. Therefore, 63 + 4s + 5s + 2s = 360 We then find the value of s: 4s + 5s + 2s = 360 - 63 11s = 297 s = 27 Finally, we solve for the remaining angles, 4s = 4*27 = 108 degrees 5s = 5*27 = 135 degrees...
*September 10, 2013*

**Math - Polygons and Quadrilaterals**

Recall that the length of a diagonal of a rectangle can be calculated by, D^2 = W^2 + L^2 or simply, we'll use the Pythagorean theorem. Substituting, 125^2 = (7x)^2 + (24x)^2 15625 = 49x^2 + 576x^2 15625 = 625x^2 x^2 = 25 x = 5 (this is the multiplier for the ratio) ...
*September 10, 2013*

**Chemistry**

Note that density is just mass per unit volume, or d = m/V Substituting, d = 24.5 grams / 3.4 Liters d = 7.21 g/L Hope this helps~ :3
*September 10, 2013*

**Chemistry**

I'll give you the steps on how to solve: (1) Get the molecular weights (MW) of MgCO3 and MgO. -> I think you know how to do this one, you just go to periodic table and find the masses of the individual atoms and add them according to the chemical formulas. (2) Let x = ...
*September 10, 2013*

**Math**

(a) If the number is even, it is divisible by 2. If the number ends with 0 or 5 (the last digit), it is divisible by 5. If the number ends with 0, it is divisible by 10. (b) If the sum of the digits of a number is divisible by 3, it is divisible by 3. For instance, 4320: 4+3+2...
*September 9, 2013*

**MATHS**

True. One way to check is of course to plot the given function. You'll see it has an axis of symmetry at y-axis. Another way is to replace x with -x. If the resulting function is the same as the original, it has an axis of symmetry at the y-axis. Like, in the given ...
*September 9, 2013*

**calculus 2**

*sorry I forgot to add + C on the answer. ^^; Anyway, in your answer that you showed us, there's no x multiplier in the second term. I think that's the only wrong term and the other terms are correct. :3
*September 6, 2013*

**calculus 2**

∫ (63x(cos(x))^2) dx 63 ∫ x(cos(x))^2 dx Recall that cos^2 x is also equal to (1/2)(1+cos(2x)): 63/2 ∫ x(1+cos(2x)) dx 63/2 ∫ x + x cos(2x) dx First term is easy, it becomes: 63/2 ∫ x dx = (63/4)x^2 For the second term, we use integration by parts...
*September 6, 2013*

**CHEMISTRY HELP! D;**

Br2 + 2 H2O + SO2 -> 2 HBr + H2SO4
*August 28, 2013*

**Chemistry**

I think this was asked before: w ww.jiskha.c om/display.cgi?id=1375933614
*August 28, 2013*

**Chemistry**

63.15 % Carbon 5.30 % Hydrogen 100 - (63.15+5.30) = 31.55 % Oxygen To do this, divide each mass percentages with the corresponding weights of the elements to get the moles of each: 63.15 / 12 = 5.26 5.30 / 1 = 5.30 31.55 / 16 = 1.97 Now, divide all by the smallest, in this ...
*August 22, 2013*

**Calculus**

To get the max velocity, first, differentiate the velocity equation with respect to time. Then equate to zero: dv/dt = 3 - 0.4t 0 = 3 - 0.4t 0.4t = 3 t = 7.5 Substitute to the original equation: v = 3t-0.2t^2 v = 3(7.5) - 0.2(7.5)^2 v = ? Or you may also want to plot the ...
*August 19, 2013*

**math**

2x^2 - 5x + k What we can do here is to get the discriminant. For a quadratic equation with form ax^2 + bx + c = 0, the discriminant is equal to b^2 - 4ac The value of discriminant for a perfect square (which therefore has equal or double roots) is equal to zero. Substituting...
*August 15, 2013*

**maths**

We can further transform the given equation in such a way that the numerical coefficient of x^2 is 1. That is, by dividing all terms by 2. In this form, recall that the sum of roots is equal to negative of the numerical coeff of x, and the product of roots is equal to the ...
*August 15, 2013*

**maths-correction**

*sorry I mean sum = -b/a, and thus R = -b/(4a) . But the answer's still the same since it is squared.
*August 15, 2013*

**maths**

ax^2 + bx + c = 0 x^2 + (b/a)x + (c/a) = 0 For quadratic equations with this form, the sum & product of roots are: sum = b/a product = c/a Let R = one root Let 3R = the other root (according to the problem) Substituting to sum & product equations, R + 3R = b/a R(3R) = c/a from...
*August 15, 2013*

**maths**

Recall that for a quadratic equation that is in the form x^2 + bx + c = 0 the sum of the roots is equal to -b, and the product of roots is equal to c. Therefore, we change the form of the given equation by this form, 4x^2 + px +5 = 0 x^2 + (p/4)x + 5/4 = 0 Then we set up the ...
*August 15, 2013*

**maths**

Recall that for a quadratic equation that is in the form x^2 + bx + c = 0 the sum of the roots is equal to -b, and the product of roots is equal to c. Therefore, we change the form of the given equation by this form, kx^2 + 4x + k^2 - 21 = 0 x^2 + (4/k)x + k - 21/k = 0 The ...
*August 15, 2013*

**math**

The given equation follows the general equation for circles, which is (x - a)^2 + (y - b)^2 = r^2 where (a,b) = the point where the center of the circle lies r = radius From the equation, (x + 3)^2 + (y + 5)^2 = 16 r^2 = 16 r = 4 units Recall that the circumference of a circle...
*August 14, 2013*

**math help**

Let x = the third number It says that the average of 2P, 3Q and x is equal to S. Therefore, (2P + 3Q + x)/3 = S Getting x, 2P + 3Q + x = 3S x = 3S - 2P - 3Q hope it helps :)
*August 14, 2013*

**Math**

OMG I'm sorry I'm thinking about x-axis! Sorry about that.
*August 12, 2013*

**Math**

First, try plotting (-3,1) on a graphing paper. You'll see it's in the 2nd Quadrant. When you reflect it on the y-axis, the new point will be on the third quadrant (where both x & y coordinates are negative). Therefore the new point is at (-3,-1). Hope this helps~ :)
*August 12, 2013*

**Math**

*sorry I mean, V = (2.5)^3
*August 12, 2013*

**Math**

V = s^3 SA = 6*s^2 Just substitute the given length of one side of the cube. V = (1.5)^3 = ? (units in cubic inches) SA = 6*(2.5)^2 = ? (units in square inches)
*August 12, 2013*

**math**

To do this, you have to work backwards. That is, starting from the $15 left. Note that she spent 2/3 of her money and had $15 left. Therefore, this $15 is actually 1/3 of the money she had: 1/3 of something = 15 To do this, just divide 15 by 1/3: 15 / (1/3) = 15*3/1 = $45 And ...
*August 12, 2013*

**Chemistry(science)**

I think you mean "methane"? If it is... Methane's chemical formula is CH4. To get the moles of methane, we first get its molar mass by adding the masses of C and H. There are C atoms and 4 H atom: CH4 = 12 + 4*1 = 16 g/mol Then we divide the given mass by the ...
*August 12, 2013*

**math**

Let x = number of Ryan's stickers Let y = number of Tony's stickers From the first statement, (2/3)x = (3/4)y From the second statement, x - 48 = y + 48 Then we solve for x and y. There are many ways to solve this system, but let's do substitution. To do ...
*August 12, 2013*

**math**

Represent the unknown with variables: Let x = amount of premium grade gasoline sold in gallons Let x+420 = amount of regular grade gasoline sold in gallons (according to the third statement) Then we set up the equation. We know that the total worth of gasoline sold is 10,957. ...
*August 12, 2013*

**math**

Recall the point-slope form: y - y1 = m(x - x1) where (x1, y1) = a point on the line m = slope or the gradient In the problem, we have a gradient or slope = 3, and point (-3,3) on the line. Substituting, y - 3 = 3(x - (-3)) y - 3 = 3(x + 3) y = 3x + 9 + 3 y = 3x + 12 Note that...
*August 12, 2013*

**maths-correction2**

**Ahhh I'm really sorry about this, I'm so careless! Really, I should be the one recalling how to factor sum of cubes lol. :p This is the last. I think you mean ax^2 +bx + c = 0. You can further transform this equation in such a way that the numerical coefficient of x^...
*August 11, 2013*

**maths**

Let m = one of the roots Let 3m = the other root (according to the condition given) Recall that for x^2 + bx + c, the sum of the roots is equal to -b, and the product of roots is equal to c. Therefore, m + 3m = -(-20) 4m = 20 m = 5 (one root) 3m = 15 (the other root) c = ...
*August 11, 2013*

**chem**

Half-filled as well as completely filled, give -higher stability (high stability is achieved when the d orbital is filled or half-filled, while half-filling the s orbital); and -lower energy to the atom (there is greater electron-electron repulsion if s orbital is filled when ...
*August 11, 2013*

**chem**

Yes.
*August 11, 2013*

**chem**

1. Recall that the formula for converting deg F to deg C is C = (5/9)*(F - 32) Substituting, C = (5/9)*(189 - 32) C = (5/9)*(157) C = 87.2 deg Celsius To convert to Kelvin, K = C + 273.15 K = 87.2 + 273.15 K = 360.37 Kelvin 2. K = C + 273 K = -248.6 + 273.15 K = 24.55 Kelvin (...
*August 11, 2013*

**math**

= 100005000562512500625 Just type it on a calculator.
*August 10, 2013*

**Math**

The formula for calculating the sum of consecutive number is S = n*(a1 + an) / 2 where n = number of terms a1 = first number an = last number Since it is from 1 to 100, n = 100. Substituting, S = 100*(1+100)/2 S = 5050 Hope this helps~ :)
*August 10, 2013*

**Chemistry-correction**

*shocks it's in MOLALITY. @_@ Please disregard the above post! Molality is moles of solute per kilogram solvent. Thus we can say there are 1.33 moles of CH2O in 1000 g of H2O. To get the moles of H2O, we divide the mass (1000 grams H2O) by its molar mass. molar mass of H2O...
*August 10, 2013*

**Chemistry**

Methanal is also formaldehyde, which has a chemical formula of HCHO (or CH2O). Molarity is moles of solute per liter of solution. Thus we can say there are 1.33 moles of CH2O in 1 L of solution. To get the mole fraction, we also need to get the moles of H2O. To do this, we get...
*August 10, 2013*

**ADVANCED AMC8 GEOMETRY QUESTION/MATH**

Note that an equilateral triangle is a triangle where all lengths of the sides are equal. If you revolve the triangle about its altitude (or the height), you'll generate a cone (just try to imagine or draw the figure). Therefore, the height of the cone is equal to the ...
*August 9, 2013*

**chemistry**

Air is a mixture of several gases. But the most abundant is Nitrogen and Oxygen. Their mole percent in air is: N2 = 78% O2 = 21% Ar = 1% *Actually the 1% here is not entirely Argon, but Argon is the most abundant in that 1%. Note that these values are NOT EXACT, but is just an...
*August 7, 2013*

**Math**

(5-7)(-8+4)/2-(-6) (-2)(-4)/2-(-6) 8/2 - (-6) 4 + 6 10 or if the whole 2-(-6) is in the denominator, (5-7)(-8+4)/(2-(-6)) (-2)(-4)/(2+6) -8/8 -1 I'm not sure how they got -33. Probably there's typo error or something...
*August 7, 2013*

**Math**

Note that is only possible if x is any real number less than or equal to zero: x <= 0 Therefore, the answer is [D] Nonpositive. Note nonpositive is different from negative numbers, as nonpositive includes zero, while Negative numbers does not include zero. (Zero is neither ...
*August 7, 2013*

**geometry**

I think we need to see the figure (because no dimensions are given)...
*August 6, 2013*

**math**

First, represent the unknown with variables. Let x = amount of money that Mary paid Let (2 1/4)x = amount of money that Kate paid (according to the problem) Then we set up the equation. We know that the total amount that they paid is $195,000, therefore: x + (2 1/4)x = 195000 ...
*August 6, 2013*

**math**

15x^2 + 7xy - 2y^2 (3x + 2y)(5x - y)
*August 6, 2013*

**chemistry**

4 covalent bonds. The formula of methane is CH4, and the covalent bonds are shared between Carbon (central atom) and the four Hydrogen atoms.
*August 4, 2013*

**Chemistry**

Ga3+ The atomic number of neutral Ga is 31. Atomic number is equal to the number of electrons if the atom is neutral. Since it has a charge of 3+, it means it lost 3 electrons. Therefore, 31 - 3 = 28. Writing the e config: (recall aufbau principle) Ga : 1s2 2s2 2p6 3s2 3p6 4s2...
*August 4, 2013*

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