Sunday

February 7, 2016
Total # Posts: 1,926

**Chemistry**

∆H for what reaction...? Write the balanced reactions: C + O2 ---> CO2 ; ∆H = -393.7 kJ/mol C CO + 1/2 O2 ---> CO2 ; ∆H = -283.3 kJ/mol CO If the problem asks for ∆H of formation for CO, we can make the second reaction become: CO2 ---> CO + 1/2...
*April 20, 2015*

**Algebra**

Represent the unknowns: Let x = one piece Since according to the problem, the other piece is 5 times as long as the first one, Let 5x = other piece Since their total length must be 24 ft, x + 5x = 24 6x = 24 x = 24/6 x = 4 ft. 5x = 20 ft.
*April 20, 2015*

**Science**

One of the formulas for uniformly accelerated motion (UAM): h = vo*t - (1/2)gt^2 Ball falls freely, so initial velocity (vo) is zero: h = 0 - (1/2)(-9.8)(0.5^2) h = 1.225 meters Since we're looking for the terminal velocity (vf) we can use the formula, vf^2 - vo^2 = 2gd vf...
*April 20, 2015*

**Algebra**

Let x = Meg's age According to the problem, Jill is 2 years younger than Meg: Let x - 2 = Jill's age And it was also said that Beth is half as old as Meg: Let (1/2)x = Beth's age
*April 20, 2015*

**Algebra**

Let x = suggested amount of donation If b is the number of bracelets given away, and every person who makes the suggested donation amount will be given one bracelet, then b is also the number of people donated. Therefore, the total collected amount is the number of people ...
*April 20, 2015*

**Science (Chemistry)**

"Like dissolves like" is a general rule in solubility. Water is a polar molecule. Its structure is not symmetric, and there is polarity between its elements that compose it - the electronegativity difference between H and O is significantly large. Ionic molecules are...
*April 20, 2015*

**Math**

No it's not 8. But you're almost correct, you just forgot to divide it by 2. :) From your solution, p = 2l + 2w 30 = (2 * 11) + 2w 30 = 22 + 2w Put the 22 (from the right side of equation) to the left side, but by doing so, you must change its sign to its opposite. It...
*April 20, 2015*

**algebra**

Let x = width Let y = length Area of rectangle is length x width, so A = xy 912 = xy Perimeter of rectangle is 2*(length + width), so P = 2(x + y) 124 = 2(x + y) 62 = x + y Now that you have two equations tow unknowns, we can solve for x and y. From the second equation, we can...
*April 20, 2015*

**physics**

P = ρgh where P = pressure (in Pa) g = acceleration due to gravity = 9.8 m/s^2 h = height (in meters) Note that 1 bar = 100000 Pa. Substituting, 100000 = (600)(9.8)(h) h = ? Hope this helps~ `u`
*April 19, 2015*

**Redox Reaction**

Write the redox reaction: Mn2+ + BiO3- --→ Bi3+ + MnO4− Balance this redox reaction. Write first the half-reactions: Reduction: BiO3- ---> Bi3+ (charge is changed from 5+ to 3+) Oxidation: Mn2+ ---> MnO4- (charge is changed from 2+ to 7+) Balance them by ...
*April 19, 2015*

**Algebra (check my work?)**

1. Yes 2. Yes 3. Let n = number of 4th grade swimmers The ratio of 4th grade swimmers to the total swimmers is 5:16 or 5/16. The total number of swimmers is 80. Therefore, n/80 = 5/16 If you solve this, you'll have n = 25 swimmers (4th grade) hope this helps~ `u`
*April 17, 2015*

**pre-calc - JAI**

Sn = n(1+3n)/2 Therefore, S1: 2 = 1(1 + 3(1))/2 S2: 2+5 = 2(1 + 3(2))/2 S3: 2+5+8 = 3(1 + 3(3))/2 They are all true/equivalent for S1, S2, and S3.
*April 17, 2015*

**math**

If you want an aquarium in shape of a cube with volume of 8000, then use the formula for volume of cube to find the length of one side: V = s^3 where s = side length Substitute, 8000 = s^3 s = cuberoot(8000) s = 20 inches Well, if you have to draw this on a graphing paper, you...
*April 17, 2015*

**pre-calc**

It's difficult to show Gaussian elimination process here. But the answers should be, x = 1, y = -4 and z = -2
*April 17, 2015*

**phyiscs**

Modified/simplified continuity equation: S1*v1*ρ1 = S2*v2*ρ2 where S1 and S2 = entrance and exit cross-sectional area v1 and v2 = entrance and exit velocity ρ1 and ρ2 = initial and final density Assuming density of water is constant, we can cancel ρ1 ...
*April 16, 2015*

**Science**

Let's have some definitions: Element - the simplest substance made up of one type of atom that cannot be broken down by any chemical means. It can be converted to other elements by nuclear methods, though. Examples are Na, Ca, Mg. Molecule - group of atoms bonded together...
*April 16, 2015*

**Math**

Separate them as such: 6x + 5y = 7x + 3y and 7x + 3y = 2(x + 6y - 1) Simplify both equation: Eqn(1): 6x + 5y = 7x + 3y 6x - 7x = 3y - 5y -x = -2y x = 2y Eqn(2): 7x + 3y = 2(x + 6y - 1) 7x + 3y = 2x + 12y - 2 7x - 2x = 12y - 3y - 2 5x = 9y - 2 We can multiply Eqn(1) by -5 so ...
*April 16, 2015*

**physics class**

Pressure is force (in Newton) per unit area (in m^2): P = F/A The force here is the weight of the ball, so we must find first the weight of the ball: W = mg where m = mass (kg) g = acceleration due to gravity = 9.8 m/s^2 Substitute the values: W = 5 * 9.8 W = 49 N Therefore ...
*April 16, 2015*

**analytical geometry**

Use distance formula: d = sqrt[(y2 - y1)^2 + (x2 - x1)^2] Their distances from one point to (-3,p) must be the same, so sqrt[(-1 - p)^2 + (7 - (-3))^2] = sqrt[(-4 - p)^2 + (4 - (-3))^2] Square both sides: (-1 - p)^2 + (7 + 3)^2 = (-4 - p)^2 + (4 + 3)^2 1 + 2p + p^2 + 100 = 16...
*April 16, 2015*

**math**

There are a lot of ways doing these. Mine might be a long way, there might be a shorter way. Anyway, let the contents of each gallon be represented in this format: (12-gallon bucket) - (7-gallon bucket) - (6-gallon bucket) Fill the 12-gallon bucket. Leave the others empty. So...
*April 16, 2015*

**Math**

(1) In arithmetic sequence, we just add the common difference, d = 0.25, to a term to get the next term. Therefore, a1 = 16.5 a2 = 16.5 + 0.25 = 16.75 a3 = 16.75 + 0.25 = 17.0 ...and so on. (2) General formula for arithmetic sequence: an = ao + (n-1)d where an = nth term ao = ...
*April 16, 2015*

**Math**

F = S/w
*April 16, 2015*

**math plz help**

Yes, both are correct. `u`
*April 15, 2015*

**ALGEBRA 2 (LOGARITHMIC FUNCTIONS)**

For the next questions, they are all solved with the same method. So I'll guide you to solving #1, then try solving the others by following these steps. We need to find an equation in the form y = ab^x that passes through the points (1,6) and (2,36). What we'll do is ...
*April 15, 2015*

**ALGEBRA 2 (LOGARITHMIC FUNCTIONS)**

I'll solve for the first five problems. You have to recall some laws of exponents for these. (1) 3^(x+1) = 27^(x+3) Note that we can rewrite 27 as power of 3: 27 = 3^3. Thus, 3^(x+1) = (3^3)^(x+3) You can distribute the '3' in 3^3 to (x+3). 3^(x+1) = 3^(3(x+3)) 3^(...
*April 15, 2015*

**Algebra 2**

(a) "Z" is distinctly different than the other: I think that means you have to count both of them, as if they're different letters. There are five letters in total. Therefore, 5! = 120 ways (b) "Z" is repeated twice in the word FUZZY. Thus, 5! / 2! = 60...
*April 15, 2015*

**math -check**

Yes, all the equations you wrote are correct. :) I don't know what window setting means too, and I don't have a graphing calculator. But I think window setting looks like in table (rows,columns) format? I'm not really sure. ^^;
*April 15, 2015*

**Math**

Yes it's B. This is another example of conditional probability. Note that there are four vowels here: U, I, O, E. And there are six letters total. So, P(vowel) = 4/6 Then you spin again. The probability of getting a P: P(P) = 1/6 Thus, P(vowel, then P) = 4/6 * 1/6 = 4/36...
*April 15, 2015*

**Math**

No it isn't. It was said that time varies inversely as the rate: t = k/r where t = time (hours) r = rate (mph) k = some constant If we solve for the constant, k, k = r*t and this k is the same for all. Therefore if we have two different values for time and rate, r1 * t1 = ...
*April 15, 2015*

**Math**

Mass, m, is varies inversely as acceleration, a: m = k / a where k some constant. since f is the constant of variation, we substitute f for k: m = f / a
*April 15, 2015*

**integral**

Well the derivative of sec(x) = sec(x) tan(x) dx, as it's one of the formulas usually memorized. So the integral of sec(x) tan(x) dx = sec(x). But if you want a longer method, we let sec(x) = 1/cos(x) and tan(x) = sin(x) / cos(x). Substituting, ∫ sec(x) tan(x) dx &#...
*April 15, 2015*

**Precalculus**

Yeah, you have to draw two different triangles for them. It's easier to solve this if you draw them. Anyway, we let arcsin(8/17) be equal to some angle, A. And we let arctan(4/3) be equal to some angle, B. In your drawing of two triangles, label these angles as A and B. We...
*April 15, 2015*

**chemistry**

At STP, T = 0 C or 273 K and P = 1 atm or 101.325 kPa. Assuming the gas ideal, we can use the formula: P1 * V1 / T1 = P2 * V2 / T2 where P = pressure V = volume T = absolute temperature (in K) subscripts 1 and 2 = initial and final properties respectively substituting, 103 * 5...
*April 15, 2015*

**calculus (steps and explanation plz)**

y'' = 6x Integrate: y' = 3x^2 + c1 Since it was said that it has a horizontal tangent at (1,1), then we let y' (the slope) be equal to 0: 0 = 3x^2 + c1 0 = 3(1)^2 + c1 0 = 3 + c1 c1 = -3 Integrate y' further (and substitute c1 = -3): y' = 3x^2 - 3 y = x...
*April 15, 2015*

**math word problems**

Raul's appointment started at 9:30 AM according to the problem: Raul - 9:30 AM After 17 minutes, Timothy arrived. That is, at 9:47 AM. But it was said that this time is 8 minutes BEFORE his actual appointment. Therefore, we add 8 minutes to it: Timothy - 9:55 AM Tyson'...
*April 15, 2015*

**SCIENTIFIC NOTATION**

What we'll do is divide 1.3 x 10^8 by 8.8 x 10^5: 1.3 x 10^8 / 8.8 x 10^5 We can rewrite 1.3 x 10^8 such that the exponent of 10 is 5. To do this, move the decimal point 3 places to the right. Why 3 places? It's because 8-5 = 3: 1.3 x 10^8 = 1300 x 10^5 Then, 1300 x 10...
*April 15, 2015*

**math plz help**

Well it's a conditional probability. You have to multiply the probability of the first event to the probability of the second event for this kind of problem. If the question asked for the probability of choosing a red OR a blue marble, then their probabilities are added. ...
*April 15, 2015*

**math plz help**

Total marbles = 43 P(red) = 8 / 43 Since it was replaced, the total number of marbles is the same for the second choosing of marble. P(blue) = 12 / 43 Probability of getting a red, then a blue: 8/43 * 12/43 = 96/1849 (letter D)
*April 15, 2015*

**ALGEBRA PLSSSSSS**

To get the inverse, what you'll do is: (1) let f(x)=y, and replace x with y and y with x: f(x) = (8 - 2x)^2 y = (8 - 2x)^2 x = (8 - 2y)^2 (2) solve for y, and substitute back the y=f(x): x = (8 - 2y)^2 sqrt(x) = 8 - 2y sqrt(x) - 8 = -2y y = (sqrt(x) - 8) / (-2) y = (8 - ...
*April 15, 2015*

**geometry/trig**

Let x = original side length (ladder-wall) Let y = original side length (ladder-floor) Well yeah. The new length of the side of the triangle (where ladder touches the wall) is x - 8. The new length of side of triangle (where ladder touches the floor) is y + 16. Of course, y is...
*April 15, 2015*

**math**

Let x = length Let 3/4x = width Area of rectangle is length times width. A = l * w Substituting: 432 = x (3/4x) Solve for x: 432 = (3/4) x^2 x^2 = 432 * 4/3 x^2 = 576 x = 24 ft. (length) 3/4x = 18 ft. (width) hope this helps `u`
*April 15, 2015*

**Math**

1. Not it's actually in Quadrants II and IV. In Q I and III, the coordinates of the point have the same sign. For instance, Quadrant I: (2,4) Quadrant III: (-1,-3) 2. Yes that's right. `u`
*April 14, 2015*

**PHYSICS1**

There's a problem similar to this. I'll just repost it here: Range of projectile formula: R = vo^2 sin(2θ) / g where θ = angle vo - initial velocity g = acceleration due to gravity = 9.8 m/s^2 substitute the values to get the range: R = (18^2) * sin(2*75°...
*April 14, 2015*

**physics**

Range of projectile formula: R = vo^2 sin(2θ) / g where θ = angle vo - initial velocity g = acceleration due to gravity = 9.8 m/s^2 substitute the values to get the range: R = (18^2) * sin(2*75°) / 9.8 R = ? Make sure your calculator is in Degrees mode, not ...
*April 13, 2015*

**chemistry**

You have to have the following values. These can be found in google or in textbooks: *specific heat capacity of ice (c,ice) in J/g-K *latent heat of fusion for water (Hf) in J/g *specific heat capacity of water (c,water) in J/g-K Then substitute them in the summation of all ...
*April 13, 2015*

**Math**

A. Yeah, almost. :) d = rt Since d = 72 miles and t = 1.5 hours or 90 minutes, 72 = 1.5r (if you want r to have units in miles/hour) 72 = 90r (if you want r to have units in miles/minute) B. 72 = 1.5r r = 72/1.5 r = 48 miles/hour 72 = 90r r = 72/90 r = 0.8 mile/min
*April 13, 2015*

**Math 1**

Let x = width Let x + 6 = length Area of rectangle is just width x length. Thus, A = w * l 16 = x(x+6) 16 = x^2 + 6x x^2 + 6x - 16 = 0 Factor: (x + 8)(x - 2) = 0 x = -8 (extraneous root since dimensions cannot be negative) x = 2 inches (width) x+6 = 8 inches (length) hope this...
*April 13, 2015*

**Physics**

Use the formula to get the time: x = vo,x * t where x = horizontal distance vo,x = initial horizontal velocity t = time 47.9 = 12 * t t = 47.9 / 12 t = 3.99 s Then use this formula to get the height of cliff: h = vo,y * t - (1/2)gt^2 where h = height vo,y = initial vertical ...
*April 13, 2015*

**Math**

This problem is similar to the one you posted before. Take two points. For instance, the first two points, (0,1) and (1,4). Get the slope: m = (y2 - y1) / (x2 - x1) m = (4 - 1) / (1 - 0) m = 3 / 1 m = 3 slope-intercept form: y - y1 = m(x - x1) y - 1 = 3(x - 0) Just simplify ...
*April 13, 2015*

**Math**

To do this, just add the numerical coefficient of the variable x. The numerical coefficient is the number before the variable. In this case, its 1/2 in the term 1/2x, and 2/3 in the term 2/3x. (1/2)x + (2/3)x = (3/6)x + (4/6)x = (3 + 4)/6 x = (7/6)x
*April 13, 2015*

**Math**

I will let n = x. Take two points. For instance, the first two points, (3,2) and (4,1). Get the slope: m = (y2 - y1) / (x2 - x1) m = (2 - 1) / (3 - 4) m = 1 / -1 m = -1 slope-intercept form: y - y1 = m(x - x1) y - 2 = -1(x - 3) y - 2 = -x + 3 y = -x + 3 + 2 y = -x + 5 hope ...
*April 13, 2015*

**science**

*sorry, I mean 4.5 / 129.5 = 3.47 % v/v
*April 13, 2015*

**science**

Add the volumes together: V,total = 125 + 4.5 = 129.5 m^3 Since alcohol is 4.5 m^3, the v/v % is V,alcohol / V,total = 4.5 / 129.5 * 100 = 3.6 %
*April 13, 2015*

**chemistry**

I see. No, the 12.5 g shouldn't have any denominator units. The given was only 12.5 g NaOH, and this is the mass of NaOH. You should write, [ 12.5 g NaOH * (1 mol NaOH / 40 g NaOH) ] / [ 625 mL * (1 L / 1000 mL) ] = 0.500 M Sorry for the late reply. Hope this helps~ `u`
*April 13, 2015*

**chemistry**

If you mean that the 12.5 NaOH is 12.5 grams of NaOH, then your answer and solution are correct. :)
*April 13, 2015*

**math**

Let alpha = a Let beta = b Because it's easier to type a and b, than copy-pasting alpha and beta symbols. Anyway, recall that for a quadratic equation in the form y = ax^2 + bx + c The sum and product of the roots can be determined as such: y = x^2 - (sum)x + (product) Of ...
*April 12, 2015*

**PRE - CALCULUS**

Yes it's D.
*April 12, 2015*

**Math**

5 ft : 135° = x ft : 360° 5/135 = x/360 x = 40/3 ft This is the whole length of the circle or the circumference. To get the radius, C = 2πr r = C / 2π r = 40/3 / (2*3.14) r = 2.12 ft
*April 12, 2015*

**MATH**

Why is that? Anyway, let's solve for y. I'll multiply the first equation by -2 instead of 2: (5x - 4y = -3) * -2 ---> -10x + 8y = 6 (2x + 7y = 5) * 5 ---> 10x + 35y = 25 Add them together: -10x + 8y = 6 10x + 35y = 25 ---------------------- 43y = 31 y = 31/43 Now...
*April 12, 2015*

**MATH**

You're doing the elimination method right. :) But there's just some errors in multiplying. In your first equation (5x - 4y = -3), you multiplied it by 2. 5x * 2 = 10x, yes that's right. -4y * 2 = -8y, not -12y as you've typed. -3 * 2 = -6, not 6 as you've ...
*April 12, 2015*

**Physics**

We use the formula: h = vo,y*t - (1/2)gt^2 where h = height vo,y = initial vertical velocity t = time g = acceleration due to gravity = 9.8 m/s^2 Since there is no vertical velocity involved, vo,y = 0. If that's not very clear, we can say that vo,y = vo*sin(angle). But the...
*April 12, 2015*

**Physics**

For the horizontal: x = vo,x * t where x = horizontal distance vo,x = initial horizontal velocity t = time x = 1100 m/s * 0.32 s x = 352 m For the vertical: h = vo,y * t - (1/2)gt^2 where h = height vo,y = initial vertical velocity (which is zero) g = acceleration due to ...
*April 12, 2015*

**WORD PROBLEM HELP**

Volume of a cylinder: V = π(r^2)(h) where π = 3.14 r = radius h = height I think this is just trial and error. For instance, take r =2 and h=6: V = π(2^2)(6) V = 3.14 * 4 * 6 V = 75.36 m^3 This is one that satisfies the requirements. Just take a value of r and h...
*April 12, 2015*

**Pre - CALCULUS**

Yes, it's D. Though it's hard to show 3x3 Cramer's rule here. ;u;
*April 11, 2015*

**Math**

Note that when a number is raised to a negative exponent, we can make its exponent positive by getting its reciprocal. Some examples: 2^-1 = 1/(2^1) = 1/2 3^-2 = 1/(3^2) = 1/9 2^-3 = 1/(2^3) = 1/8 Let's simplify each choice. A. 3^-3 * 2^3 = ( 1/(3^3) ) * 2^3 = (1/27) * 8...
*April 11, 2015*

**Math**

Speed is distance traveled over time, or v = d/t Since we're solving for time, we can rearrange the formula for time: t = d/v Substitute the values. t = 2.25 x 10^6 / 1.8 x 10^4 t = ? Units in hours. Hope this helps~ `u`
*April 11, 2015*

**Math**

Take two points from the given. For instance the first two points (-4,0) and (-2,-4). Get the slope using the formula, m = (y2 - y1) / (x2 - x1) where (x1,y1) and (x2,y2) are points on the line. Substituting, m = (0 - (-4)) / (-4 - (-2)) m = (0 + 4) / (-4 + 2) m = 4 / -2 m = -...
*April 11, 2015*

**Calculus**

Area of triangle: A = (1/2)bh When A = 97 and h = 10.5, A = (1/2)bh 97 = (1/2)(b)(10.5) b = 18.48 Differentiate area with respect to time: A = (1/2)bh dA/dt = (1/2)( h*db/dt + b*dh/dt ) Substitute the values: 4 = (1/2)( 10.5*db/dt + 18.48*2) Solve for db/dt. hope this helps~ `u`
*April 11, 2015*

**Math**

Use pythagorean theorem: c^2 = a^2 + b^2 Substitute the given values, c = slant height, a = 1/2 of length of one side of the base: 9^2 = 6^2 + b^2 b = ?
*April 11, 2015*

**pre - CALCULUS**

No it's not. Multiply -4 separately to all terms inside the bracket.
*April 11, 2015*

**pre - CALCULUS**

Yes it's B, since it can be seen clearly that the simplified version of the second equation is equal to the first equation.
*April 11, 2015*

**math - hw help. plz**

To do substitution, choose one of the equations. Then choose a variable in that equation, and express it in terms of the other variable. Finally, substitute it to the other equation. Here, let's choose the 2nd equation. 2x - y = -4/3 Then let's choose the variable y. ...
*April 10, 2015*

**Science**

Use this formula and plug in the given values: F = m * a where F = force (N) m = mass (kg) a = acceleration (m/s^2)
*April 10, 2015*

**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*