Thursday

April 2, 2015

April 2, 2015

Total # Posts: 1,600

**Chemistry**

Note that the molar mass of H2O is 18 g/mol. If you're not sure how to calculate for the molar mass, get a periodic table and look for the individual masses of the elements present in the chemical formula. For instance, in the periodic table, H has mass of 1 g O has mass ...
*April 1, 2015*

**algebra**

The equation for this relationship is a linear equation (I even used linear regression to prove it lol). To get the linear equation, we can look for the slope first. m = (y2 - y1) / (x2 - x1) where (x1,y1) and (x2,y2) are points on the line. Taking two points, for instance, (0...
*April 1, 2015*

**math**

Let x = the number of problems where he got it right since the total number of problems is 12, Let 12-x = the number of problems where he git it wrong Now, it was said that 5 points are awarded for every correct answer, or 5x and 2 points are deducted for every wrong answer, ...
*March 31, 2015*

**Math**

First we get the percentage of the students who liked the program: (218 / 245) * 100 = 88.9796 % Recall that a circle has a measure of 360 degrees. 360 degrees corresponds to the whole. Since 88.9796 % of the whole is the percentage of students who liked the program, 360 ...
*March 31, 2015*

**Algebra 2**

y = (x-5) / (x^2 - 6x + 5) Simplifying, y = (x-5) / (x - 5)(x - 1) y = 1 / (x-1) The root of the denominator is discontinuity: x = 1 : an asymptotic discontinuity The other roots (before simplification) is also a discontinuity: x = 5 : a removable discontinuity If you plot ...
*March 31, 2015*

**Chemistry**

C2H4 + O2 ---> CO2 + H2O Balancing, it becomes C2H4 + 3O2 ---> 2CO2 + 2H2O
*March 31, 2015*

**Chem**

Note that the process involved here is the phase change of ice, from solid (ice) to liquid (water). Thus, the heat involved is latent heat, not sensible heat. The latent heat of fusion of ice is approximately 334 J/g. You can look for this value in textbooks or google. Then we...
*March 31, 2015*

**physics**

We use the formula PE = mgh where PE = potential energy (J) m = mass (kg) g = acceleration due to gravity = 9.8 m/s^2 h = height (m) Substituting, 1970 = 82(9.8)(h) h = 2.45 m hope this helps~ `u`
*March 30, 2015*

**Physical science**

If v is velocity, d is distance, and t is time, therefore we can use the formula v = d/t Substituting, 55 = 68 / t t = 68 / 55 t = 1.236 hours hope this helps? `u`
*March 29, 2015*

**Chemistry**

Molality units is moles of solute per kilogram solvent. In this case, we have m = 4 moles urea / 1000 g H2O Note that water has molar mass of 18 g/mol. Getting the moles of water, we need to divide the given mass by its molar mass: 1000 g H2O / 18 g/mol = 55.56 mol H2O Since ...
*March 29, 2015*

**physics**

The gas is ideal, so we can use the formula P1 * V1 / T1 = P2 * V2 / T2 where P1 and P2 = initial and final pressures respectively V1 and V2 = initial and final volumes respectively T1 and T2 = initial and final absolute temperatures respectively Note that the temperature must...
*March 29, 2015*

**physics**

For this kind of set up, we have summation of all energy transferred equal to zero. Note that for ice, Q is different from each process: (1) from T=-5 C to T=0 ; (2) phase change of ice to water at constant T ; (3) from T=0 to final T. For Ice: (1) from T=-5 C to T=0. We use ...
*March 29, 2015*

**HARD COLLEGE CHEMISTRY**

I've posted an answer on your previous post on this similar question. Anyway, I'll just repost it here: For the equivalence point, I've already posted steps on how to work on it on the other chemistry problem you've posted. So here, I'll just guide you on ...
*March 28, 2015*

**Math**

Let t = length Let 5t = width The line that connects the opposite corners of rectangle is the diagonal, and its length can be defined as d = sqrt(l^2 + w^2) Thus, d = sqrt(t^2 + 25t^2) d = sqrt(26t^2) d = t * sqrt(26) Actually you can also use pythagorean theorem to find d, ...
*March 28, 2015*

**Math**

If you mean (6/sqrt(3)) + 2 then, first, multiply the term with the radical (squareroot sign, cuberoot sign, etc.) with radical term, in numerator and denominator: (6/sqrt(3)) * (sqrt(3)/sqrt(3)) + 2 Then simplify, (6*sqrt(3) / sqrt(3)^2) + 2 6*sqrt(3) / 3 + 2 2*sqrt(3) + 2 ...
*March 28, 2015*

**COLLEGE CHEMISTRY HARD**

Is there any volume of 0.01 M CH3COOH given? I'll just assume a value for volume, so at least you can work out on your problem by following these steps. Anyway, at equivalence point, all CH3COOH is converted to CH3COO-, thus the pH is determined by the concentration of ...
*March 28, 2015*

**college chemistry HARD**

For the equivalence point, I've already posted steps on how to work on it on the other chemistry problem you've posted. So here, I'll just guide you on the "5 mL past equivalence point". To determine the volume of the point 5 mL past the equivalence point...
*March 28, 2015*

**math**

Recall that perimeter of rectangle is two times the sum of length and width, or P = 2(l + w) If we let x as length and the value of perimeter is given, therefore, 50 = 2(x + w) Solving for w, 50 = 2x + 2w 50 - 2x = 2w w = (50 - 2x)/2 w = 25 - x hope this helps~ `u`
*March 28, 2015*

**che**

I think this problem has incomplete given. There is no data about the concentrations of NaCl and AgNO3. The concentration is usually in Molarity (mol/L) units. Without it, you can't solve for the moles of each reactant species, and you can't determine the limiting/...
*March 28, 2015*

**Chemistry**

Note that NaOH has a molar mass of 40 g/mol, and Al has a molar mass of 27 g/mol. If you're not sure how to get the molar mass, you'll need a periodic table, and add the individual masses of each element present in the chemical formula. To solve this, first we need to ...
*March 28, 2015*

**science**

In projectile motion, h,max = vo^2 sin^2 (x) / 2g where h,max = maximum height vo = initial velocity x = angle of release g = acceleration due to gravity = 9.8 m/s^2 Solving for the maximum height, h,max = 31^2 * sin^2 (35) / 2(9.8) h,max = 316.16 / 19.6 h,max = 16.13 m We can...
*March 27, 2015*

**Math**

Note that 1 meter = 0.001 kilometer 1 meter = 100 centimeters 1 meter = 1000 millimeters Thus the answers should be B and C. hope this helps~ `u`
*March 26, 2015*

**5th grade math**

1.22 times n is between 80 and 85: 80 < 1.22n < 85 Separate into two: 80 < 1.22n 65.57 < n 1.22n < 85 n < 69.672 Rewrite it again, 65.57 < n < 69.672 hope this helps~ `u`
*March 26, 2015*

**chemistry**

Ksp values vary with temperature, so you have to specific on the temperature of the system. Also, you can search for Ksp values of each in google or from your textbook. For the formulas, write first the balanced reaction. For example, for the first one, PbI2: PbI2 <---> ...
*March 26, 2015*

**Chemistry**

If you modify the formula for ideal gas (PV = nRT) a little, you'll get an expression for the density of gas: ρ = P*MM / RT where ρ = density (g/L) P = pressure (atm) MM = molar mass (g/mol) R = universal gas constant = 0.0821 L-atm/mol-K T = absolute temperature...
*March 26, 2015*

**Physics**

Formulas for projectile motion: h,max = vo^2 sin^2 (x) / 2g R = vo^2 sin (2x) / g where h,max = maximum height R = range vo = initial velocity x = angle g = acceleration due to gravity = 9.8 m/s^2 In the problem, we are asked to find vo and x, and we have two equation, so we ...
*March 26, 2015*

**chemistry**

If you modify the formula for ideal gas (PV = nRT) a little, you'll get an expression for the density of gas: ρ = P*MM / RT where ρ = density (g/L) P = pressure (atm) MM = molar mass (g/mol) R = universal gas constant = 0.0821 L-atm/mol-K T = absolute temperature...
*March 26, 2015*

**Science**

The energy is transferred and converted to other forms. For instance, if a ball is dropped to the ground, during its fall, it experiences air resistance (thus friction with air). The energy is lost to the air. If it hits the ground and you heard a sound, then some of its ...
*March 26, 2015*

**thermodynamics and statistical machenics**

You're welcome~! I'm a girl though, but it's alright~ :D
*March 26, 2015*

**thermodynamics and statistical machenics**

Under adiabatic conditions (dQ = 0), P2 / P1 = (V1 / V2)^γ where P1 and P2 = initial and final pressures respectively V1 and V2 = initial and final volumes respectively γ = heat capacity ratio = Cp/Cv Substituting, P2 / 1 = (V1 / 3*V1)^1.4 P2 = 0.2148 atm Also, under...
*March 26, 2015*

**Calculus 2 (Differential Equation)**

sqrt(1-y^2) dx - sqrt(1-x^2) dy = 0 sqrt(1-y^2) dx = sqrt(1-x^2) dy Take all term swith x to one side and all terms of y to the other side of equation: dx / sqrt(1-x^2) = dy / sqrt(1-y^2) Integrate both side. Note that, ∫(1/(sqrt(a^2 - x^2))dx = sin^-1 (x/a) + C ...
*March 26, 2015*

**algebra**

The given expression 12x^2 + 11x - 12 isn't "readily factorable". What I mean is that the factors of the constant c here are not integers or whole numbers in which when added gives an 11, so it's hard to factor it by one look (I hope that's clear?). So we...
*March 26, 2015*

**Math if my answer is correct**

I will use derivatives: h(t) = 2 + 50t - 1.862t^2 dh/dt = 50 - 3.724t 0 = 50 - 3.724t 3.724t = 50 t = 13.426 s This is the time that the ball reaches its maximum height. But the problem asks for the time the ball is above the surface of Mercury. Therefore we multiply it by 2 ...
*March 25, 2015*

**chemistry**

a. In the balanced chemical reaction 2 NH4NO3---> 2 N2 + O2 + 4 H2O The numbers before the chemical formula is called the stoichiometric coefficient. These numbers are used to make mole ratios. For instance, we can say that "For every 2 moles of NH4NO3 that reacted, ...
*March 25, 2015*

**algebra**

English alphabet has 26 letters. If letters come from the alphabet and the password does not allow repetition of the letters and is case-insensitive, then the number of possible combinations in six letters is 26*25*24*23*22*21 = 165765600 hope this helps~ `u` (I apologize if ...
*March 25, 2015*

**physics**

Since the object is in free fall, it experiences uniformly accelerated motion (UAM). We can use the formula: vf^2 - vo^2 = 2gd where vf = final velocity vo = initial velocity (in this case it's zero because freefall) g = acceleration due to gravity = 9.8 m/s^2 d = distance...
*March 25, 2015*

**Precalc**

1. I'm actually not sure what you meant by "to the cubed root", but if you mean this: log3 (cuberoot(25)) Just use a calculator to get its value. log3 (cuberoot(25)) = 0.97665 2. 1/3 logx + 2 logy^3 - 3 log(z+1) You should recall some laws of exponents. log (x^(1...
*March 25, 2015*

**Physics**

P = I*V P = (1 C / 0.09 s) * 120 V P = 1333.33 W
*March 25, 2015*

**Geometry**

area of rectangle is length x width. Therefore, we list all the factors of 128 in pairs: 1 x 128 2 x 64 4 x 32 8 x 16
*March 25, 2015*

**math.**

Break even is a point where the costs is equal to your profits. Thus, we just equate the two functions: R(x) = C(x) -5x^2 + 21x = 2x + 10 -5x^2 + 21x - 2x - 10 = 0 -5x^2 + 19x - 10 = 0 5x^2 - 19x + 10 = 0 Use the quadratic formula: x = ( -b +/- sqrt(b^2 - 4ac) ) / 2a You ...
*March 25, 2015*

**math is my answer correct**

Yes, quite close but that's correct. `u` You can use derivatives and you'll get the 337.66 meters.
*March 25, 2015*

**math**

Is the platform really 40 feet in height, not 50 feet...? Anyway, a. Yes, that value is right. b. Time it takes from platform to maximum height (I used derivatives): dh/dt = -32t + 5 0 = -32t + 5 t = 0.15625 s Time it takes from maximum height to surface of water: h = vo*t - (...
*March 25, 2015*

**math-incomplete soln**

#1: (2y+x^2+1)dy/dx + (2xy-9x^2) = 0 We can rewrite this as (2y + x^2 + 1)dy + (2xy - 9x^2)dx = 0 Check for exactness: Let M = 2xy - 9x^2 Let N = 2y + x^2 + 1 ∂M / ∂y = ∂N / ∂x ∂(2xy - 9x^2) / ∂y = ∂(2y + x^2 + 1) / ∂x 2x = 2x ...
*March 20, 2015*

**Algebra**

Recall that speed is distance traveled over time: v = d/t Represent the unknowns: Let x = speed of current Let t = time upstream Let 10-t = time downstream (since the total time is 10 hours according to the problem) Note that when the boat travels upstream, the current is ...
*March 20, 2015*

**Algebra**

Represent the unknown: Let x = original number of students Let x+6 = new number of students (after six students decided to join) It was said that the original contribution of each was reduced by $4.80 after six people joined. Thus, (224 / x) - 4.80 = 224 / (x+6) solving, [(224...
*March 20, 2015*

**Math**

The cost of a carton according to problem = c Total number of plates = bn Thus the cost per plate is, c / bn hope this helps` `u`
*March 20, 2015*

**Arithmetic Reasoning**

8 games won /24 games total = 1/3 1/3 in percentage is 33.3%
*March 20, 2015*

**pre-calculus**

P(x) = 2x^4 - 3x^3 + 3x^2 + 5x - 3 To use rational root theorem, we get all the factors of constant divided by the factors of the leading coefficient (or the term with variable of highest degree). In this case, the constant is -3, and the leading coefficient is 2. Thus, +/- 1,...
*March 20, 2015*

**math**

Let x = height of building B Let x - 180 = height of building A since their total height is 1480, x + x - 180 = 1480 Solving, 2x = 1480 + 180 2x = 1660 x = 830 ft (height of bldg B) x-180 = 650 ft (height of bldg A) hope this helps~ `u`
*March 20, 2015*

**math 5th grade**

Target: 3 meters or 300 cm First day: 0 + 40 - 2 = 38 Second day: 38 + 40 - 4 = 74 Third day: 74 + 40 - 6 = 108 Fourth day: 108 + 40 - 8 = 140 Fifth day: 140 + 40 - 10 = 170 Sixth day: 170 + 40 - 12 = 198 Seventh day: 198 + 40 - 14 = 224 Eighth day: 224 + 40 - 16 = 248 Ninth ...
*March 20, 2015*

**math**

This is hard to solve if you don't draw it. So I hope you'll draw the figure, and I'll provide the steps here. Anyway, first, I'll rename some angles. Let angle AXB = n Let angle ABX = m Let angle ABC = B Let angle ACB = C It was said in the problem that angles...
*March 19, 2015*

**algebra**

3j^3 - 5ij^2 + 210j First, we factor out the most obvious factor (which is j, since all terms contain the variable j): j (3j^2 - 51j + 210) We can also see here that the terms inside the parenthesis have a common factor of 3, thus, 3j (j^2 - 17j + 70) To factor the quadratic ...
*March 19, 2015*

**math**

Limit of sin(x)/(tan(x)*sec(x)+tan(x)*sin(x)) as x approaches 0 simplify first the expression: sin(x)/(tan(x)*sec(x)+tan(x)*sin(x)) Note that tan(x) = sin(x)/cos(x) and sec(x) = 1/cos(x). Thus, sin(x) / (sin(x)/cos(x) * 1/cos(x) + sin(x)/cos(x) * sin(x)) sin(x) / (sin(x)/cos^2...
*March 18, 2015*

**chemistry**

BaCl2 (aq) + H2SO4 (aq) ---> BaSO4 (s) + 2HCl (g) BaSO4 (s) is the white precipitate in this reaction.
*March 18, 2015*

**Chemistry**

I think it's C, but I'm not really sure. Water is a polar molecule and table salt is ionic. Water and salt are both very polar. When placed in water, NaCl is surrounded first by water molecules and then NaCl dissociates to Na+ and Cl-. They are then attracted to the ...
*March 18, 2015*

**math.**

Yes that's right. `u`
*March 17, 2015*

**chemistry**

A and C are both endothermic, since energy is required to break bonds between solute-solute molecules and solvent-solvent molecules. The step that releases energy is when the solute and solvent are mixed (letter D).
*March 17, 2015*

**Chemistry**

Viscosity is simply the resistance to flow. If there is larger viscosity, then it has greater intermolecular force. thus, olive oil has greater intermolecular force than benzene. hope this helps~ `u`
*March 17, 2015*

**math**

To solve for y, first, we must isolate the term with y to one side of the equation. We can see that on the left side of the equation, the term with y is 3y, but the left side also has -6 in it. Thus we transfer it on the right, but its sign becomes the opposite (positive in ...
*March 17, 2015*

**Math**

Recall that speed is distance traveled over time: v = d/t Represent the speeds with variables: Let x = speed of Plane A Since it was said the speed of Plane B is 300 km/h faster than Plane A, Let x + 300 = speed of Plane B When they catch up, that means that their distance ...
*March 17, 2015*

**math**

Yes, that's right. `u`
*March 17, 2015*

**chemistry**

For a general reaction, aA + bB ---> cC the equilibrium constant, Kc, is given by Kc = [products] / [reactants] = (C)^c / ( (A)^a * (B)^b ) The reaction given is: 2 NH3 ---> N2 + 3 H2 Thus, Kc = (N2) * (H2)^3 / (NH3)^2 Plug in the concentration values given, and solve ...
*March 17, 2015*

**Chemistry**

The chemical formula of aspirin is C9H8O4. The molecular weight of aspirin is therefore 180 g/mol. To get the grams of aspirin in the problem, just multiply the moles given by the molecular weight (to cancel units). Hope this helps~ `u`
*March 17, 2015*

**math**

Represent the unknowns. Since the ratio of their money shared is 5 (David) : 2(John), Let 5x = David's money Let 2x = John's money In the problem, John received $30 less than David. Thus, 2x = 5x - 30 Solving, 2x - 5x = -30 -3x = -30 x = 10 Thus, 5x = $50 (David) 2x...
*March 17, 2015*

**Chemistry**

Since the equation is already given, we just plug in the values. It was said in the problem that the reaction should proceed 8 times faster than the original at 315 K. Thus the ratio k2/k1 = 8. R is the universal gas constant = 8.314 J/mol-K All temperatures must be absolute (...
*March 17, 2015*

**Science**

Definitely it isn't a noble gas since noble gas are stable and unreactive. They can still form compounds with other elements though. Group 15 is also group 5A (Nitrogen, Phosphorus, etc.), and Group 17 is also group 7A (Fluorine, chlorine, etc.). Elements in these groups ...
*March 17, 2015*

**Science**

Yes it's B. :)
*March 17, 2015*

**Algebra**

I think you mean x^3 - 6x^2 + 8x for the equation written in the problem. No, the answer you got isn't quite right. The first factoring is correct though. To factor x^3 - 6x^2 + 8x, the first obvious factor here is x, since all terms in the expression contain x. Thus, x(x^...
*March 17, 2015*

**Math, HELP PLEASE!**

No, it isn't. In a geometric sequence, there is a fixed number multiplied by a term to get the next term. This is an example of geometric sequence: 3, 6, 12, 24, 48, ... Here, we can see that each term is multiplied by two to get the next term. 3*2 = 6 ; 6*2 = 12, and so ...
*March 17, 2015*

**math**

I just assume you want to convert the 275 liters to mL units. To convert, note that 1 L = 1000 mL. Thus to cancel units, 275 L * (1000 mL / L) = 275000 mL hope that helps? ^^;
*March 17, 2015*

**Algebra help please**

I'm not sure if that expression is 4*sqrt(400) / (4*sqrt(5)), or the fourth root (radical sign with a number four on it). If it's the fourth root, then your answer is correct. `u`
*March 17, 2015*

**Algebra**

f(x) = x^2 + 2x - 9 This is a quadratic equation. There are plenty of ways to get its maximum/minimum. One way is to graph and locate on the graph the point where max/min occurs. Another is to solve for its vertex. We can transform the equation into the form f(x) = a(x-h)^2 + ...
*March 17, 2015*

**chem**

Recall that molarity is moles of solute per liter of solution. It has mol/L (or M) units. M = n/V First, we convert the volume (100 mL) to liters units. To convert, we just divide it by 1000: 100 / 1000 = 0.1 L Since we need to calculate the moles, we rearrange the formula to ...
*March 16, 2015*

**Chemistry**

Activated complex - a species in a transition state. (not sure about this one though) Elementary reaction - a reaction in which the stoichiometric coefficients in the balanced chemical reaction is equal to the exponents used the rate equation, or (if that isn't very clear...
*March 16, 2015*

**Chemistry**

Heterogeneous reaction - a chemical reaction in which the reactants are in different phases. Some examples are, Liquid-solid: alkylation with AlCl3 catalyst Gas-liquid: gas absorption with reaction Gas-liquid-solid: hydrogenation of liquids Homogeneous reaction - a chemical ...
*March 16, 2015*

**math**

Note that the equation is in slope-intercept form, y=mx+b where m is the slope and b is the y-intercept In the equation y=-1/3x + 3, therefore the slope is -1/3.
*March 16, 2015*

**Algebra**

To get the x-intercept, let y = 0 and solve for x: -3x + 4y = -12 -3x + 4(0) = -12 -3x = -12 x = 4 Thus x-intercept is at (4,0) To get the y-intercept, let x = 0 and solve for y: -3x + 4y = -12 -3(0) + 4y = -12 4y = -12 y = -3 Thus y-intercept is at (0,-3) hope this helps~ `u`
*March 16, 2015*

**Maths**

Average weight is the total weight divided by the number of people. To find the average weight of boys, we first look for the total weight of all (boys + girls), and the total weight of the girls. Weight of all (boys + girls): 44 * 50 = 2200 kg Weight of girls: 40 * (50 - 40) ...
*March 15, 2015*

**Calculus**

Substitute y = 3x - 7 to x^2*y: x^2 * (3x - 7) 3x^3 - 7x^2 Then differentiate with respect to x, and equate to zero (since we're looking for maximum/minimum): 9x^2 - 14x = 0 x(9x - 14) = 0 x = 0 x = 14/9 Note that if x = 0, the minimum product of x^2 * y is zero. But if x...
*March 15, 2015*

**Calculus**

*Correction* I'm sorry, the one I did is not called L'hopital's rule. That is just another technique of finding limits (dividing numerator and denominator by the variable with highest degree). L'hopital's rule is different, for it uses separate ...
*March 15, 2015*

**Calculus**

lim [ 6x^2 / (200-4x-kx^2) ] as x->infinity = 1/2 Notice that the numerator and denominator has the same highest degree of x. Therefore, we can use the L'hopital's rule. To do this, we divide both numerator and denominator by x^2: lim [ (6x^2 / x^2) / (200-4x-kx^2)/...
*March 15, 2015*

**Algebra**

(1) Yes (2) Yes (3) Hmm how did you arrive with your answer, because I'm getting, = 70 + 40 + 2(30 + .29) = 110 + 2(30.29) = 110 + 60.58 = 170.58 or perhaps there is typo or missing info? And I'm also curious with your use of 'm' units.
*March 15, 2015*

**Physics**

P,abs = P + pgh P = (1.01*10^5 Pa) + (1025 kg/m^3)*(9.8 m/s^2)(15 m) P = 101000 + 150675 P = 251675 Pa Check the significant figures. Hope this helps~ `u`
*March 14, 2015*

**Calc**

∫ (2x+1)/(x+1) dx We can separate this term into two terms by taking each term in the numerator: ∫ (2x)/(x+1) + 1/(x+1) dx For the term on the right, ∫ 1/(x+1) dx = ln |x+1| For the term on the left, Let u = x+1, thus x = u-1, and dx = du Replacing, 2 ∫...
*March 14, 2015*

**Calculus check**

Yes, that's right. `u`
*March 14, 2015*

**maths**

To get the lateral surface area, simply multiply the base perimeter by the height, 25 cm * 40 cm = ? hope this helps~ `u`
*March 14, 2015*

**chemistry**

First, we write the balanced reaction: 2 AgNO3 + K2S -> 2 KNO3 + Ag2S Recall that molarity is moles per liter solution, or M = n/V Then we get the number of moles of K2S by simply multiplying the volume (should be in L units) by the concentration (Molarity has units mol/L...
*March 13, 2015*

**Math**

(1) You have to recall some laws of exponents. 15 * 3^(y+1) - 243 * 5^(y-2) = 0 3 * 5 * 3^(y+1) - 3^5 * 5^(y-2) = 0 5 * 3^(y+1+1) - 3^5 * 5^(y-2) = 0 5 * 3^(y+2) = 3^5 * 5^(y-2) 3^(y+2) / 3^5 = 5^(y-2) / 5 3^(y+2-5) = 5^(y-2-1) 3^(y-3) = 5^(y-3) The only number that will ...
*March 13, 2015*

**Math Functions (if i have correct answer)**

Max height - yes, we got approximately the same answer Time - the time you got is the time where the ball reached the maximum height. The question asks for the total time (the time the ball is above the surface of Mercury), therefore you should multiply it by 2, so it would ...
*March 13, 2015*

**math**

f varies inversely with g: f = k * (1/g) where k is some constant. f=20 when g=4: 20 = k * (1/4) k = 20 * 4 k = 80 f=? when g=10 f = 80 * (1/10) f = 8 Hope this helps~ `u`
*March 12, 2015*

**Algebra**

an = ao + (n-1)d where an = the nth term ao = the first term n = number of terms d = difference between two consecutive terms Substituting the given, (i) a6 = 13 (here, n=6, an=13) 13 = ao + (6-1)d 13 = ao + 5d (ii) a10 = 25 (here, n=10, an=25) 25 = ao + (10-1)d 25 = ao + 9d ...
*March 12, 2015*

**chemistry**

We write the reaction: HC2H3O2 + KOH -> KC2H3O2 + H2O The products are potassium acetate (salt) and water.
*March 12, 2015*

**chemistry**

Assuming the gas is ideal, for a fixed volume of gas, we can use the Gay-Lussac Law, which states that Pressure is directly proportional to Temperature of gas: P = kT where P = pressure k = some constant T = temperature (in Kelvin) If we're given sets of values for ...
*March 12, 2015*

**math**

Recall that speed is distance traveled over time: v = d / t Rearranging to get t, t = d / v For the two trips, the distance traveled is the same, while the speed and time of travel are different. We represent each time traveled as such: Let t1 = time traveled (towards Rocky ...
*March 12, 2015*

**Separation processes**

If the "low" volatility in the question means it is CLOSE to 1 (not equal to 1), then the answer is letter 'D' or 'separation of components is difficult. If it said "exactly equal to 1", then it's 'B'. But since it doesn't ...
*March 12, 2015*

**help**

Because half-life means final amount becomes 50% of original, therefore, after another half-life time, the final amount becomes 25% of original. Well if you look at the problem, all you have to do is multiply the the half-life 12.3 years by 2, which is 24.6 years. But if you ...
*March 11, 2015*

**Math**

Represent the unknowns. Let x = length since the width is 3/4 of the length, Let (3/4)x = width Recall that the area of rectangle is just width multiplied by the length, A = w * l Substituting, 432 = (3/4)x * x 432 = (3/4)x^2 432 * 4/3 = x^2 576 = x^2 Get the square root of ...
*March 11, 2015*

**Chemistry help please**

Yes, that's right. The oxidation number of P in P2O3 is +3.
*March 11, 2015*

**Math**

This problem looks similar to the other math problem posted here. OwO Anyway, first represent the unknowns. Let x = length since the width is 2/3 of the length, Let (2/3)x = width Recall that the area of rectangle is just width multiplied by the length, A = w * l Substituting...
*March 11, 2015*

**Chemistry ( I NEED HELP, PLEASE!!!, IM DESPERATE!)**

First, we balance the chemical reaction: 2 Na2O2 + 2 H2O → 4 NaOH + O2 Then, we need to determine the molar masses of Na2O2 and O2 in order to convert them to moles. To get them, we need the mass of each element in the formula and add. In the periodic table, Na = 23 and ...
*March 11, 2015*

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