Sunday

April 26, 2015

April 26, 2015

Total # Posts: 1,752

**Math**

What's the question? Anyway, 35 = 18 cannot be.
*April 10, 2015*

**Math**

The problem asks which of the following covers SOME of the solution for the inequality x ≥ 3. The answers are A, C and D. In letter A, x > 3. They share almost all solutions, but it excludes the number 3. In letter B, x < 0. Definitely they don't share any ...
*April 10, 2015*

**8th grade math**

Let x = minutes Company A: f(x) = 25 , for 0 < x ≤ 100 f(x) = 25 + 0.50(x-100) , for x > 100 Company B: f(x) = 50 , for any value of x
*April 9, 2015*

**Chemistry**

Summation of all heat is zero. Q,aluminum + Q,water = 0 The formula for Q is Q = mc(T2-T1) where m = mass (g) c = specific heat capacity (J/g-K) T = temperature (K) Substitute the values. Note that the final Temperature (T2) is the same for both: [mc(T2-T1)],aluminum + [mc(T2-...
*April 9, 2015*

**Math**

Yes, it's B.
*April 9, 2015*

**Algebra**

p+5, 4p+3, 8p-2 If they are in arithmetic sequence, then have a common difference or (4p + 3) - (p + 5) = (8p - 2) - (4p + 3) Solving for p, 4p + 3 - p - 5 = 8p - 2 - 4p - 3 3p - 2 = 4p - 5 3p - 4p = -5 + 2 -p = -3 p = 3 To get the value of each term just substitute the value ...
*April 9, 2015*

**pre - CALCULUS**

I assumed that (1 + tan^2 u)(1 - sin^2 u) = 1 Note that (1 + tan^2 u) = sec^2 u. [pythagorean identity] And that (1 - sin^2 u) = cos^2 u. [pythagorean identity, from cos^2 u + sin^2 u = 1] Thus, ( sec^2 u )( cos^2 u )= 1 Note that sec u = 1 / cos u, (1 / cos u)^2 (cos^2 u) = 1...
*April 9, 2015*

**pre - CALCULUS**

If you mean, Monthly service charge: $8.80 Per therm service charge 1st 25 therms: $0.6686/therm Over 25 therms: $0.85870/therm therefore for the first 25 therms in a month, 8.80 + 0.6686(25) = ? and for 45 therms in a month, 8.80 + 0.6686(25) + 0.85870(45-25) = ? For x therms...
*April 9, 2015*

**Chemistry**

I assumed that 45 mL of NaOH, and that "02 M" is 0.02 M HCl. Write the balanced equation: HCl + NaOH ---> NaCl + H2O Then get the moles of HCl by multiply the volume by the molarity: M = n/V n = V*M n = 30 mL * 0.02 M n = 0.6 mmol HCl Since in the reaction it'...
*April 9, 2015*

**pre - CALCULUS**

cot θ ∙ sec θ = csc θ Note that cot θ = cos θ / sin θ, and sec θ = 1 / cos θ: cos θ / sin θ ∙ 1 / cos θ = csc θ 1 / sin θ = csc θ Note that 1 / sin θ = csc θ. Thus: csc θ = csc θ
*April 9, 2015*

**chemistry**

If the problem asks for the specific heat capacity, then we just use the formula, Q = mc(T2-T1) where Q = heat (J) m = mass (g) c = specific heat capacity (J/g-K) T2 = final temperature (K) T1 = initial temperature (K) Substituting, 1500 = 100 * c * (50 - 20) c = ? Now solve ...
*April 9, 2015*

**math**

n < 20
*April 9, 2015*

**math**

Let n = average capacity Let n + 1 = capacity of E Therefore, their average is (2 + 5 + 3 + 3 + (n + 1))/5 = n Solving for n, (14 + n)/5 = n 14 + n = 5n n - 5n = -14 -4n = -14 n = -14/-4 n = 7/2 n = 3.5 ton n+1 = 4.5 ton (capacity of E) hope this helps~ `u`
*April 9, 2015*

**Precal**

x^2 - y^2 - 2x + 4y - 6 = 0 First, rearrange the terms as such: x^2 - 2x - y^2 + 4y = 6 We can put parenthesis to separate all terms with x from all terms with y. (x^2 - 2x) + (-y^2 + 4y) = 6 Notice that the coefficient of y^2 is negative. We can factor out -1 so we'll ...
*April 8, 2015*

**chemistry**

We have to look first for the specific heat capacity and latent heat of vaporization for water. These values can be found in textbooks or in google. Specific heat of water, c = 4.18 J/g-K Latent heat of vaporization, Hv = 2256 J/g The first process is heating of the water from...
*April 7, 2015*

**Trigonometry**

Diameter = 24 in Radius = 12 in (a) angular speed (ω) = ? We use the formula: v = ω r Substituting, 15 mi/hr = ω * 12 in Note that 1 mile = 63360 inches, and 1 hour = 60 min: 15 mi * (63360 in / mi) / (1 hr * 60 min / hr) = ω * 12 in 15840 in / min = ω...
*April 7, 2015*

**math**

Perimeter of square: P = 4s where s = side length. Solve for P of square: P = 4 * 6.75 P = 27 It was said that the P of rectangle is 35.54 inches longer than P of square. Thus, P (rectangle) = 27 + 35.54 P (rectangle) = 62.54 round off to nearest tenth: = 62.5 in
*April 7, 2015*

**Physics!**

Formula for power given the current and voltage: P = IV Substituting, P = 5.0 * 120 P = 600 Watts Note that Watts is also Joules / second. Thus to get the energy, we multiply the power by the time: P = E/t E = Pt E = 600 J/s * 42 s E = 25200 J hope this helps~ `u`
*April 7, 2015*

**Math**

Numbers greater than or equal o 3: 3, 4, 5, 6 So, yes it's 4/6.
*April 7, 2015*

**math**

(4n-1)^2 = 16 Get the squareroot of both sides: 4n - 1 = +/- 4 (+): 4n - 1 = 4 4n = 5 n = 5/4 (-): 4n - 1 = -4 4n = -4 + 1 n = -3/4 hope this helps~ `u`
*April 7, 2015*

**cheminstry**

Assuming ideal gas, we can use Charles Law: V1 / T1 = V2 / T2 where V = volume T = absolute temperature (K) It's just direct substitution. I'll do (a): V1 / T1 = V2 / T2 2.5 / 300 = 5 / T2 Solve for the new temperature (T2): 2.5(T2) = 300(5) T2 = 1500 / 2.5 T2 = 600 K ...
*April 7, 2015*

**Math**

Yes, it's B.
*April 7, 2015*

**Chemistry**

Sodium...? Sodium what? Anyway, I'll just provide steps: (1) Write the balanced chemical reaction. Actually I'm not sure with the reaction of this, because of the 'sodium'. Normally it would be Sodium Hydroxide, Sodium Chloride solution, etc. (2) Calculate the ...
*April 7, 2015*

**math**

Divide and simplify them: 2 inch / 20 feet 1 inch / 10 feet Scale is 1 inch = 10 feet
*April 7, 2015*

**Science**

Resistance is 4.0 Alpha...? I think you mean 4.0 Ohms (Ohm has symbol of capital letter of Omega, Ω). Alpha (α) is different, it is the temperature coefficient of resistance. Anyway, you use the formula: I = V/R where I = current (Ampere) V = voltage (Volts) R = ...
*April 7, 2015*

**calculus**

First, we get the boundaries of the arch. The boundaries of the arch has y-coordinate of zero (when it crosses the x-axis), thus, 0 = cos(x/4) cos^-1 (0) = x/4 π/2 = x/4 x = 2π -π/2 = x/4 x = -2π Thus, boundary is from -2π to 2π. Actually, there ...
*April 7, 2015*

**Math**

The problem says that he increases the distance he runs by 15%, not by 15 miles. First, we get how much distance is increased in the first week, by getting the 15% of the original distance he can cover: 15% of 8.5 can be translated mathematically to 0.15 x 8.5 which is equal ...
*April 7, 2015*

**math**

Well, you use substitution. To do substitution, you choose one of the equations, and express one of the variables in terms of the other. Actually, here, we can see that the first equation (3a = 6-b) can be readily substituted to the second equation (3a = 4-b), because of they ...
*April 7, 2015*

**ALGEBRA /116**

-5x/7 - 2 > -1 Solve for x like a normal equation: -5x/7 > -1 + 2 -5x/7 > 1 -5x > 7 -x > 7/5 Now, when you multiply both sides by a negative number (in this case, it's -1), the inequality sign changes to opposite: x < -7/5 x < -1.4 Or if that's not...
*April 7, 2015*

**algebra/116**

Plug in the value of x and y of each point in the equation of the line. If it satisfies, then that point is a solution or is located on the line. For instance, take (0,-6). In this point, x = 0 and y = -6. If you substitute x = 0 to the equation, you should get a value of y...
*April 7, 2015*

**algebra**

Note that x^-2 = 1/x^2 Therefore, (x^-3 + y^-1) / x^-2 = (1/x^3 + 1/y) / 1/x^2 = (x^2)(1/x^3 + 1/y) = (x^2 / x^3) + (x^2 / y) = 1/x + x^2/y
*April 7, 2015*

**math**

Let x = original price. The given amount is already the discounted price, therefore: original price - (13% of original price) = 870000 or x - (0.13x) = 870000 0.87x = 870000 x = 870000/0.87 x = ?
*April 7, 2015*

**math**

(a) Ratio and proportion: 4 gray : 5 blue = 60 gray : x blue To solve for n, we can rewrite it in fraction: 4/5 = 60/x Cross-multiply: 4x = 60*5 4x = 300 x = 300/4 x = 75 blue tiles (b) Let n = some factor since their ratio (4:5) is always the same, we can say that 4n + 5n = ...
*April 7, 2015*

**Chemistry**

Hmm, is that really capital letter 'M' (Molarity) or small letter 'm' (molality)? Anyway, I'll just assume it's Molarity. First, we get the molar mass of KBr. You'll need a periodic table to to solve for it. Anyway, KBr has molar mass of 119 g/mol. ...
*April 6, 2015*

**Physics**

Momentum formula: momentum = mass x velocity substituting, 20 = 12 * v v = ? Units in m/s
*April 6, 2015*

**Algebra 1**

y= -x^2 + 1/2x + 2 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 y = a(x-h)^2 + k where (h,k) is the vertex. ...
*April 6, 2015*

**Physics**

The object experiences uniformly accelerated motion (UAM) so we can use the formula: vf^2 - vo^2 = 2gd where vf = final velocity vo = initial velocity g = acceleration due to gravity = 9.8 m/s^2 d = distance Since the object is in free fall, vo is zero: vf^2 - 0 = 2*9.8*3 vf^2...
*April 6, 2015*

**Physics**

Since the camera experiences uniformly accelerated motion (UAM), we can use the formula h = vo*t - (1/2)gt^2 where vo = initial velocity (m/s) h = height (m) t = time (s) g = acceleration due to gravity = 9.8 m/s^2 Since the camera is in free fall (it was dropped right before ...
*April 5, 2015*

**Math**

No it isn't A. First, we get the total or sum of the four test scores by multiplying the mean by 4: 85 * 4 = 340 Then, we subtract this by the sum of the other three given test scores to find the fourth: 340 - (81 + 83 + 85) = ? hope this helps~ `u`
*April 5, 2015*

**physics**

v = ω * r where v = linear/tangential velocity (m/s) ω = angular velocity (rad/s) r = radius (m) Since the wheels rotate at 1 rev/s (this is the angular velocity), its equivalent to rad units is 2π rad/s. And since the wheels have circumference of 2 m, the ...
*April 5, 2015*

**chemistry**

Because if you plot the second derivative, (that is, (Δ(ΔpH/ΔV)/ΔV) versus Volume), you'll see that the equivalence point corresponds to the volume where the graph crosses the x-axis (or at (Δ(ΔpH/ΔV)/ΔV) = 0). From there you can ...
*April 5, 2015*

**Physics**

First, we solve for the mass of the person. Because mass of any object is not changing or constant. We use the formula for weight: W = mg where W = weight (N) m = mass (kg) g = acceleration due to gravity = 9.8 m/s^2 substituting, 500 = m*(9.8) m = 500/9.8 m = 51.02 kg Since g...
*April 5, 2015*

**Calculus**

No need for trig substitution. We'll just do normal substitution: Let u = sqrt(x^2 - 4) Thus, we can make the following relation: u^2 = x^2 - 4 x^2 = u^2 + 4 2u du = 2x dx dx = u/x du Substituting, ∫ ( x^3 * sqrt(x^2-4) ) dx ∫ ( x^3 * u * u / x ) du ∫ ( x...
*April 5, 2015*

**PHYSICS HELP!!**

In projectile motion, we can use the formula, d = vo,x * t or d = vo cos(a) * t where d = distance traveled horizontally vo = initial velocity vo,x = initial horizontal velocity a = angle t = time Substituting, 15 = vo * cos(38) * 1.30 vo = ? hope this helps~ `u`
*April 5, 2015*

**Science**

Work is force multiplied by distance, or W = F*d Substitute the given values: W = 50 N * 5 m W = ? Units in Joules. Hope this helps~ `u`
*April 4, 2015*

**Elementary Algebra**

Note that rate is distance traveled over time, or r = d/t If you have walked 1 mile from 6:00 to 7:30 (that's 1.5 hours, right?), then your average rate is r = 1 mile / 1.5 hours r = 2/3 mph This is your average rate. And we assume this as constant. If we make a linear ...
*April 4, 2015*

**Differential Equation**

Sorry I forgot to put the constant from integration. Thus, F = e^xy + x + 2y + C
*April 4, 2015*

**Differential Equation**

(ye^xy + 1)dx + (xe^xy + 2)dy = 0 Check for exactness: Let M = ye^xy + 1 Let N = xe^xy + 2 ∂M / ∂y = ∂N / ∂x ∂(ye^xy + 1) / ∂y = ∂(xe^xy + 2) / ∂x Use chain rule to get the derivative: e^xy + xy e^xy = e^xy + xy e^xy Thus it is ...
*April 4, 2015*

**News**

Tingin ko mahirap sya ipredict kasi walang signal na magsasabi na parating na yung lindol, or something, unlike sa mga weather forecasts na kayang ipredict exactly yung time and location kung saan tatama yung bagyo, typhoon, etc. and yung lakas nito (kaya may idea tayo kung ...
*April 4, 2015*

**math**

Let x = salary Let (x-3000)/5 = cost of shoes Therefore, total salary minus his costs is the 2/5 of his salary left: x - 3000 - (x-3000)/5 = (2/5)x [ x - 3000 - (x-3000)/5 = (2/5)x ] * 5 5x - 15000 - x + 3000 = 2x 2x - 12000 = 0 2x = 12000 x = 6000 hope this helps~ `u`
*April 2, 2015*

**math**

Let x = Daisy stickers Let y = Henry stickers According to the problem: (1/4)y = (2/3)x And understanding the first statement, we can say that Henry has more stickers than Daisy: y - x = 135 Substituting the second equation to first (with y = 135 + x); (1/4)(135 + x) = (2/3)x...
*April 2, 2015*

**physics**

Assuming the air is ideal, you can use the formula P1 * V1 / T1 = P2 * V2 / T2 where P1 and P2 = initial and final pressures respectively (psi) V1 and V2 = initial and final volumes respectively (ft^3) T1 and T2 = initial and final absolute temperatures respectively (Rankine)
*April 2, 2015*

**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*