Thursday

April 17, 2014

April 17, 2014

Total # Posts: 1,491

**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~ :)

**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...

**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...

**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 heig...

**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...

**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...

**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 ...

**geometry**

I think we need to see the figure (because no dimensions are given)...

**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 ...

**math**

15x^2 + 7xy - 2y^2 (3x + 2y)(5x - y)

**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.

**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...

**chemistry**

From the given mole fraction, we can say that there are 0.15 moles of NaOH per 1 mole solution (NaOH + H2O). Therefore, the moles of H2O alone is equal to 1 - 0.15 = 0.85 mol H2O We first find the molarity. Molarity is the moles of solute per liter of solution. We now have the...

**maths-typo**

*I mean the roots are p+1 and q-1. Just a typo error. Sorry about that. :3

**maths**

Recall that in a quadratic equation, x^2 - (sum of roots)x + (product of roots) = 0 or if we let a & b the roots, x^2 - (a+b) + (a)(b) = 0 From the given equation, we can see that the constant term is factored, which is (p+1)(q-1). Now, let's assume that the roots are p+1 ...

**Physics**

When you're riding a city bus sometimes there are no seats left and you have to stand. Why are there vertical and horizontal metal hand bars on the bus? Use the concept of inertia and Newton's 1st law

**Physics**

When you're riding a city bus sometimes there are no seats left and you have to stand. Why are there vertical and horizontal metal hand bars on the bus? Use the concept of inertia and Newton's 1st law

**Physics**

An 8 kg ball is moving at 4 m/s. Work is done on the ball to give it a speed of 12 m/s. What is the ball's initial kinetic energy? What is the ball's final kinetic energy? What work was done on the ball?

**math**

To do this, just multiply the total number of people by the fraction which are artists: 360*3/8 = 135 hope this helps~ :)

**algebra**

-2(x+3) - 5(x-4) -2x - 6 - 5x + 20 -7x + 14

**Prisms**

Recall that the area of a prism is just area of the base times height. In this case, the base is the triangle. Since the lengths of side of triangle are given, we use Heron's formula to get first the area: A = √(s(s-a)(s-b)(s-c)) where a, b & c = lengths of side of t...

**Conversions**

Area of a trapezium: A = (b1 + b2)*h/2 where: b1 & b2 = lengths of the parallel sides h = height or the distance between the parallel sides Substituting, 130 = (10+14)*h/2 260 = 24*h h = 260/24 h = ? (units in m) Hope this helps~ :)

**math**

#4. Represent the unknowns with a variable. Let x = smallest side Let x + 5 = larger side (according to the 2nd statement) Let 2x - 1 = largest side (according to the 2nd statement) Then setup the equation. Recall that the perimeter of a triangle is just the sum of the lengths...

**math**

#1. First, we represent the unknown using variables. Let x = Ed's age Let 59 - x = father's age (since according to the first statement, the sum of their ages is 59) Then we setup the equation. According to the second statement, Father's age = 4*(Ed's age) - 11...

**math**

(a.) 3m/2 = 45 1/2 Note that to solve this, we should first change the mixed number (the 45 1/2) to an improper fraction. To change, multiply the whole number (the 45) to the denominator of the fraction (which is 2), then add the numerator to the product: 45 1/2 = (45*2 + 1)/2...

**math**

(a.) x/5 - 2 = 4 x/5 = 4 + 2 5*(x/5) = 5*(6) x = 30 (b.) 5m - 2/5 = 3/5 5m = 3/5 + 2/5 5m = 5/5 (5m)/5 = 1/5 m = 1/5 (c.) x/4 + 1/4 = 3/4 x/4 = 3/4 - 1/4 4*(x/4) = 4*(2/4) x = 2 (d.) y/8 - 7/8 = 3/8 y/8 = 3/8 + 7/8 8*(y/8) = 8*(10/8) y = 10

**correction-math**

IGNORE THE ABOVE POST LOL. I shouldn't have used greater than and less than signs! @_@ From the first statement, x = 7 * 5 - 11 x = 35 - 11 x = 24 From the second statement, x = 11 * 2 + 5 x = 22 + 5 x = 27 Sorry about that. I don't know what I'm thinking lol. ^^; ...

**math**

I'm not so sure if the problem requires the domain (all possible values of the number). Or if the problem requires only one value of the unknown. Let x be the number. From the first statement, x < 7 * 5 - 11 x < 35 - 11 x < 24 From the second statement, x > 11 ...

**Chemistry**

Recall that density of a material can be solved by d = m/V where: m = mass of material V = volume of material Note that the volume of a cylinder is given by V = pi*(r^2)*h where: r = radius (which is 1/2 of the diameter) h = height Substituting, V = 3.14*[(2.50/2)^2]*5.50 V = ...

**Chemistry**

#1. Recall that the density of a material is just d = m/V where: m = mass V = volume Also, the volume of a rectangular solid is given by V = l*w*h where: l = length w = width h = height Substituting, d = 80 / (3*6*4) d = 80 / 72 d = 1.11 g / cm^3 No, it will NOT float because ...

**Maths**

Since we cannot draw the figure here, you can draw the figure yourself. Note that a right pyramid is a pyramid with a square base and the apex (the tip of the pyramid) is aligned directly at the center of the base. Now, draw an line from the apex to the center of the base, whi...

**Maths**

Since we cannot draw the figure here, you can draw the figure yourself. Note that a right pyramid is a pyramid with a square base and the apex (the tip of the pyramid) is aligned directly at the center of the base. Now, draw an line from the apex to the center of the base, whi...

**math**

By using elimination method, one of the variables must be eliminated by adding the two equations. -3x + 4y = 6 9x - 12y = -18 We first choose the variable we want to eliminate. In here, let's choose x. To eliminate x, the term with variable x must have the same numerical c...

**math**

First, we solve for the area of the rectangles. Recall that the area of a rectangle is just A = L*W where L = length and W = width. Area of large rectangle: A = 16*12 A = 192 ft^2 Area of small rectangle: A = 4*8 A = 32 ft^2 Finally, we divide: 192/32 = 6 sheets of plywood Hop...

**Math**

121/11(6+5) First evaluate the operation inside the parenthesis. 121/11(11) If the whole 11(11) is under the fraction bar, we then multiply it. 121/121 = 1

**phy**

[Q1] Note that for an ideal gas, the volume of the gas is directly proportional to the temperature of the gas (Charles' Law). Just think of it as when you have a balloon of certain volume, and then you heated it (temperature increases), the balloon will expand (volume also...

**chemistry**

Assuming the gas is ideal, we use Charles' Law to relate the relationship between Temperature & Volume of gas: V1/T1 = V2/T2 where: T1 = initial temperature of gas (in K) T2 = final temperature of gas (in K) V1 = initial volume of gas V2 = final volume of gas substituting,...

**chemistry**

Assuming the gas is ideal, we use Charles' Law to relate the relationship between Temperature & Volume of gas: V1/T1 = V2/T2 where: T1 = initial temperature of gas (in K) T2 = final temperature of gas (in K) V1 = initial volume of gas V2 = final volume of gas *note that to...

**chemistry**

Assuming the gas is ideal, we use Gay-Lussac's Law to relate the relationship between Temperature & Pressure of gas: P1/T1 = P2/T2 where: T1 = initial temperature of gas (in K) T2 = final temperature of gas (in K) P1 = initial pressure of gas P2 = final pressure of gas *no...

**Physics**

Here, CSA of first rod = C CSA of first rod = D Thermal Conductivity of first wire = a Thermal Conductivity of 2nd wire = b Let the length of the two wires be L Temperature difference at the ends be ∆T Now by law thermal conduction for first conductor ∆Q/∆t =...

**math**

Christamas card costs $0.75 each and postage stamps costs $0.39 each. If you have $3.00 only to spend on sending 2 cards to your friends, how much money will be left after sending the cards

**Chemistry**

N2 + 3 H2 -> 2 NH3 Just use their stoichiometric coefficients (number before the chemical's name) from the balanced chemical reaction to make ratios and solve for the unknown. In this case, 2 moles of NH3 are produced for every 3 moles of H2. Thus, 7.5 moles H2 x (2 mol...

**chemistry**

Divide the mass given in the problem by the atomic weight of Copper from the period table. hope this helps~ :)

**Math**

First we represent the unknowns: Let x = daughter's present age Let 2x = mother's present age According to the problem, 20 years ago, the mother was three times older than her daughter. Thus, 2x - 20 = 3(x - 20) Solving for x, 2x - 20 = 3x - 60 2x - 3x = -60 + 20 -x = ...

**math**

Number of hours spent on studying = 4 Total number of hours (in a day) = 24 Percent of her day spent on studying is equal to: 4/24 * 100 = ? hope this helps~ :)

**math**

Yup that's right. :)

**math**

Percent of the theater filled is equal to the number of tickets sold over the total seats: 100/250 * 100 = ? hope this helps~ :)

**Math**

I think this problem has a figure given, but it can't be shown. Well I think it's ok. Acceleration is equal to change in velocity over time. Note that is a vector quantity, so it is represented by magnitude and direction. In the problem, since it slows down, it is term...

**Math**

I am a number on the hundreds chart. The sum of my digits is 9. My tens digit is 4. What number am I?

**physics**

Hello jai. (lol we're using the same name) :p Anyway, I think the statement is wrong that it forgot to mention the direction where the car travels. Velocity is equal to displacement over time, which is a vector quantity, thus it shall be stated using magnitude and directio...

**physics**

Your friend says his remote control car travels at a velocity of 1.5 m/s. What is wrong with that statement

**algebra**

8y + 7x = -21 8y = -21 - 7x y = -21/8 - (7/8)x

**math**

C. less than eight

**General Chemistry**

What is the molality of a solution composed of 38.0 g of cane sugar (C12H22O11) dissolved in 175 g of water?

**Algebra 2**

14 + 3x – 7 = 7x + 7 – 4x 7 + 3x = 7 + 3x 0 = 0 It is ALWAYS true.

**Physics**

Tan(b)=31.4 /100

**Physics**

Tan(b)=31.4 /100

**Please help quick! Maths**

It's difficult to show here the graphical method, but there are many ways on how to do this. One way is to choose three random values of x (for example, 0, 1, and 2) and get the corresponding y value by substituting these values to both equations, and plot the points on a ...

**Please help quick! Maths**

It's difficult to show here the graphical method, but there are many ways on how to do this. One way is to choose three random values of x (for example, 0, 1, and 2) and get the corresponding y value by substituting these values to both equations, and plot the points on a ...

**Please help quick! Maths**

To do substitution method, we choose an equation and express one of the variables in terms of the other, and finally substitute this to the other equation. In this case, let's choose the first given equation and express x in terms of y: x - 2y - 5 = 0 x = 2y + 5 then we su...

**College Algebra**

1. fog(x) = 2 /[(7/x) - 3] simplifying, 2x/(7 - 3x) Domain: all real numbers except 3, 0 and 7/3 2. 2^(1-9x) = e^(2x) get ln of both sides: ln 2^(1-9x) = ln e^(2x) (1-9x)*(ln 2) = 2x (1-9x)/(2x) = 1/(ln 2) 1/(2x) - 9/2 = 1/(ln 2) 1/(2x) = 1/(ln 2) + 9/2 2x = 1/[1/(ln 2) + 4.5]...

**9th grade math**

3 5/8 - 1 3/4 To do this, first we convert the mixed numbers to improper fractions. To convert we multiply the denominator (the number under the line) by the constant then add this answer to the numerator (number above the line), while retaining the denominator. Doing this, 3 ...

**algebra**

3x^3 + 9x^2 + 6x 3x(x^2 + 3x + 2) 3x(x+1)(x+2)

**algebra**

7z^2 + 21z - az - 3a 7z(z + 3) - a(z + 3) (7z - a)(z + 3)

**chemistry**

Heat of sublimation. It is approximately equal to 2850 J/g H2O.

**math**

2x(z - 1) + 8x 2xz - 2x + 8x 2xz + 6x

**math**

-8 1/8 = (6 1/2)p so first, we change the mixed numbers into improper fractions. To convert them, we take the product of the denominator and the constant then add it to numerator. This answer is the new numerator, while retaining the denominator: 8 1/8 = (8*8 + 1)/8 = 65/8 6 1...

**practical math**

assuming the gas is ideal, we can use the Charles' Law: V1 / T1 = V2 / T2 where V1 = initial volume of gas T1 = initial temp of gas V2 = final volume of gas T2 = final temp of gas substituting the values to the equation, 0.20 / 333 = V2 / 533 V2 = 0.20*533/333 V2 = 0.32 cu...

**Calc**

f(x) = e^(−3x) + 5e^(4x) Note that the derivative of e^x is equal to e^x times the derivative of the exponent with variable x: d/dx (e^x) = e^x dx applying this, f'(x) = -3e^(-3x) + 20e^(4x) : First derivative f''(x) = 9e^(-3x) + 80e^(4x) : Second derivative

**algebra 117**

i interpreted it as: 3/(x^2 + x - 6) substituting x = 3, 3/(9 + 3 - 6) 3/6 1/2

**math**

2 log x - log 3 = 2 recall some laws of exponents. Note that we can rewrite the first terms as: 2 log x = log (x^2) Also, when two log terms of the same base are being subtracted, we can rewrite it as the quotient of the terms inside the log: log (x^2) - log (3) = log [(x^2)/3...

**math**

let x = your age 400 - 2x = 236 400 - 236 = 2x 164 = 2x x = 82

**Math**

I. 3x + 7y + 5 = 0 4x - 3y - 8 = 0 To solve, we can either use substitution or elimination method. For substitution, we choose one equation and represent one variable in terms of the other. Let's choose the first equation, and represent x in terms of y: 3x + 7y + 5 = 0 3x ...

**math30**

substitute the value: pH = -log[H+] 2.5 = -log[H+] -2.5 = log[H+] note that log has a base of. Thus to get [H+], raise both sides of equation by 10 (to cancel the log): 10^(-2.5) = [H+] [H+] = 3.2 x 10^(-3)

**algebra**

*I had a correction for the last question you posted: Q: mang pedring wanted to construct a square table such that the length of its side is 30 cm longer than its height. What expression represents the area of the table? Suppose the table is 90 cm high what would be the area? ...

**Integral math**

Note that the given equation is a parabola that opens upward. The only point on the graph where the tangent line is parallel to the x-axis is at the vertex of the parabola, where it is at minimum. The slope of the tangent line at this point is zero (y=0). To get this point, we...

**Integrated Math 1**

f(x)g(x)= x^1999 * (2x - x^5) note that to multiply terms with the same base (in this case, the base is the variable x), we just add their exponents: 2*x^(1999+1) - x^(1999+5) 2x^2000 - x^2004 if it's just a typo, the answer is A. :)

**Integrated Math 1**

f(x) = -1 - 6x^2 - x^3 g(x) = -2 - 4x^2 f(x)-g(x) = -1 - 6x^2 - x^3 - (-2 - 4x^2) -1 - 6x^2 - x^3 + 2 + 4x^2 1 - 2x^2 - x^3 it's A. :)

**algebra_correction**

*wait. I had a correction: If table is 90 cm high, then the length of square is 120 cm. Substituting this to the equation for area, A = 90^2 + 60(90) + 900 A = 14400 cm^2 *sorry about that! The x value substituted must be 90, not 120. x__x ..haha wow ang galing naman,, fellow ...

**algebra**

Let x = height of table Let x+30 = length of table Recall that area of square is given by A = L^2 where L = length of one side. substituting, A = (x+30)^2 A = x^2 + 60x + 900 If table is 90 cm high, then the length of square is 120 cm. Substituting this to the equation for are...

**algebra**

probably the height in the problem is the length of the leg of the table or how high the table is.

**algebra**

*sorry i mean length = x + 30

**algebra**

Let x = height of the table since length is 30 cm longer than the height, then height = x + 30

**trigonometry**

First note that a whole circle measures 360 degrees or 2pi radians. The 3/2pi radians is just 3/4 of 2pi, Thus we can say that the length of arc given (the 60 ft) is just 3/4 of the circumference of the circle. If 60 is just 3/4 of the whole, then 60/(3/4) = 80 ft is the circu...

**algebra**

let x = length of ladder if you draw the figure, you actually form a right triangle, where the ladder is the hypotenuse, and the wall is the height. Thus, we use trigonometry. sin (angle) = opposite / hypotenuse sin 75 = 34 / x x = 34 / (sin 75) x = 34 / 0.966 x = 37.27 ft hop...

**Pre-Calc/Math**

recall that sin^2 x + cos^2 x = 1 therefore, we use this substitute the sin^2 x at the right side of equation: cos(x) + 1 = 1 - cos^2 x cos(x) = -cos^2 x cos(x) + cos^2 (x) = 0 factoring, cos(x) [1 + cos(x)] = 0 *for cos(x) = 0, the x values allowed are π/2 and 3π/2....

**Math**

Note that slope-intercept form is in the form y = mx + b where m = slope b = y-intercept Thus, y - 3 = -5(x + 1) y = -5x - 5 + 3 y = -5x - 2

**Math**

recall slope-point form: y - y1 = m(x - x1) where m = slope (x1, y1) = point on the line thus, y - 5 = 2(x - (-1)) y = 2(x + 1) + 5 y = 2x + 2 + 5 y = 2x + 7 hope this helps` :)

**Math**

recall slope-point form: y - y1 = m(x - x1) where m = slope (x1, y1) = point on the line thus, y - 5 = 2(x - (-1)) y = 2(x + 1) + 5 y = 2x + 2 + 5 y = 2x + 7 hope this helps` :)

**6th g-math**

let p = number of packs of mech pencil the total amount he could spend is 1.5p + 5.5 and this amount cannot be greater than (but can be equal to) $10, since his only money is $10. Thus, 1.5p + 5.5 _< 10 it's A.

**Elem Math**

Nope. Multiplying the lengths of sides gives you the volume. To get the surface area of a rectangular prism, SA = 2(L*W + L*H + W*H) where L = length W = width H = height therefore, #1. SA = 2(6*4.25 + 6*3.5 + 4.25*3.5) SA = 122.75 ft^2 #2. SA = 2(4*2.5 + 4*2.33 + 2.5*2.33) SA...

**Precalculus**

120 degrees and 300 degrees

**science**

first, write the chemical reaction: NH3 + H2SO4 -> (NH4)2SO4 then we balance this: 2NH3 + H2SO4 -> (NH4)2SO4 then we find the weight of NH3 and (NH4)2SO4. We can do this by getting each atomic mass of the element in the chemical formula, and add them. It can be found on ...

**trig**

let x = height of tree tan(angle) = x/27 tan(26) = x/27 x = 0.488*27 x = 13.17 = 13 m

**algebra 1**

(z - 4)/(z + 7) = 1/5 cross-multiplying, 5(z - 4) = z + 7 5z - 20 = z + 7 4z = 27 z = 27/4

**Geometry**

tan A * tan B = 1

**math**

sorry, i could not understand #15. #16. you have to plot this. But if you already know some properties of circle (in terms of its equation), you can skip plotting. The equation is a graph of circle, with center at (-6,-4) and radius = 6. The center is the position of source, a...

**circles**

At first, I was having difficulty understanding the given. I thought the PQ, PR and QR are the lengths of the triangle, but they are actually the arc (angle measure). Anyway, to get x, we know that the measure of a circle is 360 degrees. We get the sum of arcs PQ, PR and QR an...

**math**

3.62 x 10^7

**circles and arcs**

At first, I was having difficulty understanding the given. I thought the PQ, PR and QR are the lengths of the triangle, but they are actually the arc (angle measure). Anyway, to get x, we know that the measure of a circle is 360 degrees. We get the sum of arcs PQ, PR and QR an...

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