Tuesday
February 9, 2016

Posts by Jai

Total # Posts: 1,926

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

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

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

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

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

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

calculus 2
*sorry I forgot to add + C on the answer. ^^; Anyway, in your answer that you showed us, there's no x multiplier in the second term. I think that's the only wrong term and the other terms are correct. :3
September 6, 2013

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

CHEMISTRY HELP! D;
Br2 + 2 H2O + SO2 -> 2 HBr + H2SO4
August 28, 2013

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

maths-correction2
**Ahhh I'm really sorry about this, I'm so careless! Really, I should be the one recalling how to factor sum of cubes lol. :p This is the last. I think you mean ax^2 +bx + c = 0. You can further transform this equation in such a way that the numerical coefficient of x^...
August 11, 2013

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

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

chem
Yes.
August 11, 2013

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

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

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

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

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

ADVANCED AMC8 GEOMETRY QUESTION/MATH
Note that an equilateral triangle is a triangle where all lengths of the sides are equal. If you revolve the triangle about its altitude (or the height), you'll generate a cone (just try to imagine or draw the figure). Therefore, the height of the cone is equal to the ...
August 9, 2013

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

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

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

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

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

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

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

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

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...
August 4, 2013

maths-typo
*I mean the roots are p+1 and q-1. Just a typo error. Sorry about that. :3
August 3, 2013

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 ...
August 3, 2013

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
July 11, 2013

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
July 11, 2013

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?
July 11, 2013

math
To do this, just multiply the total number of people by the fraction which are artists: 360*3/8 = 135 hope this helps~ :)
July 9, 2013

algebra
-2(x+3) - 5(x-4) -2x - 6 - 5x + 20 -7x + 14
July 9, 2013

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 ...
July 9, 2013

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~ :)
July 9, 2013

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...
July 8, 2013

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...
July 8, 2013

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...
July 8, 2013

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
July 8, 2013

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. ^^; ...
July 8, 2013

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...
July 8, 2013

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 = ...
July 8, 2013

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 ...
July 8, 2013

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, ...
July 8, 2013

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, ...
July 8, 2013

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 ...
July 4, 2013

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 ...
July 3, 2013

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
July 3, 2013

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...
July 3, 2013

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...
July 3, 2013

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...
July 3, 2013

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 *...
July 3, 2013

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...
June 3, 2013

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
April 24, 2013

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 ...
March 18, 2013

chemistry
Divide the mass given in the problem by the atomic weight of Copper from the period table. hope this helps~ :)
March 11, 2013

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...
March 6, 2013

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~ :)
March 6, 2013

math
Yup that's right. :)
March 6, 2013

math
Percent of the theater filled is equal to the number of tickets sold over the total seats: 100/250 * 100 = ? hope this helps~ :)
March 6, 2013

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 ...
March 6, 2013

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?
December 6, 2012

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 ...
December 4, 2012

physics
Your friend says his remote control car travels at a velocity of 1.5 m/s. What is wrong with that statement
December 4, 2012

algebra
8y + 7x = -21 8y = -21 - 7x y = -21/8 - (7/8)x
October 20, 2012

math
C. less than eight
October 20, 2012

General Chemistry
What is the molality of a solution composed of 38.0 g of cane sugar (C12H22O11) dissolved in 175 g of water?
September 18, 2012

Algebra 2
14 + 3x – 7 = 7x + 7 – 4x 7 + 3x = 7 + 3x 0 = 0 It is ALWAYS true.
August 29, 2012

Physics
Tan(b)=31.4 /100
August 27, 2012

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 ...
August 26, 2012

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 ...
August 26, 2012

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 ...
August 26, 2012

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...
August 14, 2012

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 ...
July 26, 2012

algebra
3x^3 + 9x^2 + 6x 3x(x^2 + 3x + 2) 3x(x+1)(x+2)
July 25, 2012

algebra
7z^2 + 21z - az - 3a 7z(z + 3) - a(z + 3) (7z - a)(z + 3)
July 25, 2012

chemistry
Heat of sublimation. It is approximately equal to 2850 J/g H2O.
July 24, 2012

math
2x(z - 1) + 8x 2xz - 2x + 8x 2xz + 6x
July 24, 2012

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