Wednesday

May 4, 2016
Total # Posts: 406

**maths**

How many Sq metres is there in a area of 200cm x195cm x10cm deep?
*November 20, 2015*

**science**

If the absolute temperature ooh 6 inches cubed of a gas decreases by a factor of 2, what will be the new volume? How do set up this problem and solve it?
*November 18, 2014*

**Maths**

the length of a rectangle L metres and the width of the rectangle is W metres. Each measurement is correct to the nearest cm. Find, in terms of L and W the difference between the lower bound and the upper bound of the area of the rectangle.
*November 12, 2014*

**physics**

A 2.41 kg ball is attached to a ceiling by a 1.86 m long string. The height of the room is 3.38 m. The acceleration of gravity is 9.81 m/s 2 . What is the gravitational potential energy associated with the ball relative to a) the ceiling? Answer in units of J b) the floor c)a ...
*December 6, 2013*

**Calculus**

Find the number b such that the line y = b divides the region bounded by the curves y = 4x2 and y = 1 into two regions with equal area. (Round your answer to two decimal places.)
*November 18, 2013*

**math**

Let the folders cost f. Let the rulers cost r. Sarah paid: 8f + 3r Lea paid: 8r + 3f Sarah paid 1.25 more than Lea. 8f + 3r = 1.25 + 8r + 3f 5f = 1.25 + 5r f = 0.25 + r The rulers cost: r = 0.45 .: f = 0.70 Each folder costs 70 cents. Check. 8*(0.70) + 3*(0.45) = 6.95 1.25 + 8...
*November 1, 2013*

**Physics**

A satellite moves in a circular orbit around the Earth at a speed of 5.3 km/s. Determine the satellite’s altitude above the surface of the Earth. Assume the Earth is a homogeneous sphere of radius 6370 km and mass 5.98 × 1024 kg. The value of the universal ...
*October 29, 2013*

**algebra**

Redistribute for like terms. = (8+8)m3+(-3+3)m2+(1-4)m+(-5-2) = ...
*October 10, 2013*

**Calculus**

f(x) is continuous over the domain. [-3,3] f(x) is differential. f'(x) = 3x2 -9 f(x) has two equal value points on the independent axis. f(-3) = f(3) = 0 Therefore Rolle's Theorem Applies .: Exists c such that f'(c)=0 Solve for c: 0 = 3c2 - 9 ...
*October 10, 2013*

**Physics**

The centre of gravity is the point around which the weighted distribution of mass of the body sums to zero. Its relative placement within the body is independent of the orientation of the whole body; though of course it is affected by redistribution of parts of the body. ...
*October 9, 2013*

**Math-Algebra**

Again, use Pythagorus. d2 = 152 + 152 d = 15√2
*October 9, 2013*

**Math-Algebra**

Use Pythagorus. 122 = 22 + h2
*October 9, 2013*

**Chemistry**

Use: E = hc/λ Where: Planck Constant: h = 6.62606957(29)×10−34J∙s Speed of Light: c = 2.99792458×10+9m∙s-1 Wavelength: λ = 0.130m
*October 8, 2013*

**math**

a) S'(t) = dS(t)/dt S'(t) = ((d5t/dt)(t2+1) - 5t d(t2+1)/dt)/(t2+1)2 S'(t) = (5(t2+1) - 10t2)/(t2+1)2 S'(t) = (5-5t2)/(t4+2t2+1)
*October 6, 2013*

**Physics**

m1 × 3.10m/s2 = m2 × 2.00m/s2 m2 = 1.55 × m1
*October 6, 2013*

**chemistry**

Use V = m / (w c) Where: V : volume m : mass w : molecular mass c : concentration
*October 6, 2013*

**Calculus**

Don't forget the constants of integration. ------------- A = ∫ √(a2-x2) dx Let x = a sin(θ) dx = a cos(θ) dθ A = ∫ a2cos(θ)√(1-sin2(θ)) dθ A = ∫ a2cos2(θ) dθ A = (a2/2) ∫ (cos(2θ)+1) dθ A...
*October 3, 2013*

**Calculus**

(B) You have two simultaneous equations in two variables. The original equation, and the derivative for specified values of dy/dx. When dy/dx=1/2 : 1/2 = y/(2y-x) Rearrange: 2y - x = 2y Hence: x = 0 Substitute back into y2 = 2 + xy: Therefore: y = ±√2 Answer: (0...
*October 2, 2013*

**Chemistry**

Compare to the tossing two coins. P(Head ∩ Head) = P(Head) × P(Head) = 1/4 P(Head ∩ Tail) = 2 × P(Head) × P(Tail) = 1/2 P(Tail ∩ Tail) = P(Tail) × P(Tail) = 1/4 (Note that there are two ways to toss a head and a tail.) The formation of...
*October 1, 2013*

**MATH**

Which of what following? ... And what do you think is the right one?
*October 1, 2013*

**Pre-Calculas 11**

I cannot see the diagram, so I am going to assume the new fencing is formed into an 'E' shape, with the opening pressed up against the existing fence line. That is: one long side (l), two short sides and the divider (3w). The fence length is: 800 = 3w + l So the area ...
*October 1, 2013*

**la sallle**

Three consecutive even integers are: 2n, 2n+2, 2n+4, where n is an integer. The rule is thus: 2(2n+4)/2n = (3/5)(2n+2) - 3 Rearranging gives: 0 = 6 n2 - 19n - 20 Find the integer root(s) of this quadratic. Solve for integer n. Use n to find the three consecutive even numbers.
*September 30, 2013*

**maths**

y = 7x + 21 a = 7*8 + 21
*September 30, 2013*

**maths**

Hint: The first sequence is: 1/(1+1), 2/(2+1), 3/(3+1), 4/(4+1)
*September 30, 2013*

**Dice Probability**

No. The probability of the first die rolling a 2 is 1/6. The probability of the second die rolling a 3 is 1/6. The combined probability is 1/36.
*September 30, 2013*

**Card Probability**

There are 52 cards in the deck; 13 in each of the four suits, and two of the suits are red. The four face cards in each suit are: jack, queen, king, and ace. P(face card) = 4/13 P(red) = 1/4 The events are independent. The probability of an intersection of independent events ...
*September 30, 2013*

**Probability With Cards**

The events are independent. Use: P(Ki ∩ ♥) = P(Ki)×P(♥)
*September 30, 2013*

**maths**

Hint: the sequence is: 21,22,23,24,25,...
*September 30, 2013*

**MATH**

Let N = a.bcd c = d+3 -> 3 ≤ c ≤ 9 b = c-2 -> 1 ≤ b ≤ 7 a = b+c a = 2c-2 -> 4 ≤ a ≤ 8 c = (a+2)/2 -> 3 ≤ c ≤ 5 .: c = 3, N= 4.130... c = 4, N= 6.241... c = 5, N= 8.352... Though of course the rules only fix the first ...
*September 30, 2013*

**chem-redox**

Opps. Cut and paste error. 2 Ca + Cr2O72- + 14 H+ = 2 Ca2+ + 2 Cr3+ + 7 H2O
*September 29, 2013*

**chem-redox**

In acidic aqueous solution you use water to balance oxygen and hydrogen cations to balance hydrogen. Ca = Ca{2+} + 2 ē Cr2O7{2-} + 14 H{+} + 6 ē = 2 Cr{3+} + 7 H2O ===================================================== 3 Ca + Cr2O7{2-} + 14 H{+} = 3 Ca{2+} + 2 Cr{3...
*September 29, 2013*

**physics**

Hint: What affect does horizontal velocity have on vertical fall? Use: vector displacement equation. x(t) î + y(t) ĵ = [x(0) + u(0)t] î + [y(0) + v(0)t - ½ gt^2] ĵ xt î + yt ĵ = (x0 + u0 t) î + (y0 + v0 t - ½ g t2) ĵ
*September 29, 2013*

**Math**

Check the bracket placement. ±√(10/3) = ±√(10)/√(3) = ±√(30)/3 = ±(⅓)√(30)
*September 29, 2013*

**Chemistry**

An ionic exchange reaction only occurs when dissolved ions are removed from solution as (1) a precipitate (solid), (2) a gas, or (3) form a molecule that remains in the liquid phase. Sodium- and Potassium- -Biphosphates (and -Phosphates) are soluble. Sodium- and Potassium- -...
*September 29, 2013*

**Math**

When y = 0 then x = 1. As y rises towards positive infinity, x rises towards positive infinity. As y falls towards negative infinity, x falls towards 0. There is no real value of y corresponding to any negative value of x. -∞ ≤ y ≤ +∞ 0 ≤ x ≤...
*September 29, 2013*

**Computer Science**

The main should declare and load the list structure (or object), and also a variable to hold the result. The list structure cannot be fixed length; it needs to grow arbitrarily long. You'll also need a way to input numbers into the list. Given your modular design, this ...
*September 28, 2013*

**Calculus & Vectors**

Use z = x + yi Plot on the Cartesian (x,y)-plane a) Plot (x, y) = (2, 0) b) Plot √(x^2 + y^2) = 2 c) Plot (x, y) = (5, 4) d) Plot (x, y) = (√2, -√2)
*September 28, 2013*

**math**

Yes. Exactly. (x^2 -7x -8) / (x+1) = x + (-8x -8)/(x+1) = x -8
*September 28, 2013*

**math**

Do you mean: 4 (x^2 + x) / (x-3x) = -2 (x+1) = -2x -2
*September 28, 2013*

**math**

Please be clearer. What does the bracketed 4 mean? Is everything to the right of the division sign on the denominator, or just the first x?
*September 28, 2013*

**Math**

Consider the quadratic: 9z^2 - 148z + 64 Its roots are: (148 ±√(21904-2304))/18 = (148±140)/18 .: either 4/9 or 16 Thus we can factorise the quartic: 9x^4 - 148x^2 + 64 = (9x^2 - 4)(x^2 - 16) Next, factorise each of these two quadratic terms in turn.
*September 28, 2013*

**physics**

Rearrange the equation: A = F_x / t^2 Then simply substitute the numbers: .: A = (781.25/1.45^2) N/s^2 Answer in three significant figures.
*September 28, 2013*

**Science**

You simply need to express 2.16 micrometres in 5.0 seconds as some kilometres per hour, retaining the appropriate number of significant figures during conversion. 1 μm = 1×10^–6 m 1 km = 1×10^+3 m 1 hr = 3600 s 2.15μm / 5.0s = _._ ×10^__ km/hr
*September 27, 2013*

**Physics**

Use the classical mechanic equations of force, displacement, and velocity under constant acceleration from rest. (1)... F = m a (2)... s = a t^2 /2 (3)... v = a t From (1), doubling the force will double the acceleration (for the same mass). From (2), doubling the acceleration...
*September 27, 2013*

**Significant figures**

The count of significant figures for the product is the least count of significant figures of the terms. To determine how many significant figures to use, count the significant figures of each of the terms and use the least one.
*September 27, 2013*

**chemistry**

(CH3)2NH + H2O = (CH3)2NH2{+} + OH{-} Kb = [(CH3)2NH2{+}] [OH{-}]/[(CH3)2NH] At 11.98 the contribution of OH{-} concentration from dissociated water is negligible. [OH{-}] = 10^(11.98-14.00) [(CH3)2NH2{+}] = [OH{-}] [(CH3)2NH] = 0.164M - [OH{-}] Kb = [OH{-}]^2 / (0.164M - [OH...
*September 27, 2013*

**AP CHEM**

This question is incomplete. It contains insufficient information to answer.
*September 26, 2013*

**Combinatorics**

C(4,1) C(5, 1) C(6, 1) = (4!/1!3!) (5!/1!4!) (6!/1!5!) = ...
*September 26, 2013*

**Math**

x ≤ -1
*September 25, 2013*

**Math**

6 ≤ 4 + (-2x) 2 ≤ -2x x ≤ 1
*September 25, 2013*

**chemistry**

You have 5.6 mL of NH3. There are 22.4 L per mole of gas at STP. So 5.6e-3 / 22.4 mole of NH3. Balance the equation to determine the corresponding number of H2.
*September 25, 2013*

**calculus**

ln(2) = 0.69314718... (A) P(6)/P(0) = 2 .: k_g = ln(2) /6mth (B) P(3mt) = 4000 e^{3 k_g} (C) k_d = -ln(2) /10day
*September 25, 2013*

**physics**

Given: v1 = 34.5 [cos(50°) W + sin(50°) N] km/hr v2 = 16.1 [0 W + 1 N] km/hr Let: s = 3 v1 + 0.5 v2 Find: |s| s = (3*34.5*cos(50°)) W + (3*35.6sin(50°)+0.5*16.1) N |s| = √((3*34.5*cos(50°))^2 + (3*35.6sin(50°)+0.5*16.1)^2)
*September 24, 2013*

**calculous**

cannot see figure.
*September 24, 2013*

**physics**

The same current flows through the same cross-sectional area, but with only half the diameter, P has only ____ the area. Thus it passes ___ the current. [If you halve the diameter what happens to the area?]
*September 24, 2013*

**Chemistry**

You also need the molar mass of water. Let x represent the amount of sodium sulfate in the sample. Solve these simultaneous equations: 142.05 x + 18.015 nx = 8.5 18.015 nx = 4.776
*September 24, 2013*

**vector physics**

Using the standard orthogonal unit vectors î and ĵ. Momentum of the system: 0.045*9.0 î - 0.145*7 ĵ kg∙m/s Magnitude: √((0.045*9.0)^2 + (0.145*7)^2) kg∙m/s Direction: angle measured off x-axis -arctan((0.145*7)/(0.045*9.0))
*September 23, 2013*

**Physics**

If a 100%-efficient engine transfers 100% of the fuel's energy to work then, 0% of the fuel's energy would be wasted as heat, vibration, or otherwise. If it extracts 100% of the available energy from the fuel then anything left will have 0% available energy; that will ...
*September 22, 2013*

**math**

Let the number of Zerg be z, and Borges be b. Heads: 45 = z + 4b Feet: 55 = 3z + 2b Solve the simultaneous equations. Hint: multiply the first by 2 and subtract the second, then simplify. Hint 2: multiply the second by 3 and subtract the first, then simplify.
*September 22, 2013*

**math**

Let the number of Zerg be z, and Borges be b. Heads: 45 = z + 4b Feet: 55 = 3z + 2b Solve the simultaneous equations. Hint: multiply the first by 3 and subtract the second, then simplify. Hint 2: multiply the second by 3 and subtract the first, then simplify.
*September 22, 2013*

**physics**

Solve for t to find the breaking time. 0 = 19m/s - t_b 4.6m/s^2 Substitute to find the breaking distance. d = t_b 19m/s - t_b^2 2.3m/s^2 Find the time to travel to that point. t_d = (48.2m - d) / 19m/s.
*September 22, 2013*

**Physics**

Given: speed of v = 30[m/s] radius of r = 25[m] Use: Centipetal-acceleration of: a_c = v^2/r
*September 22, 2013*

**Chemistry- that is correct.**

Yes. 34m/s = 34m/s * 1000mm/m * 60s/hr = 2040000mm/hr ≈ 2.0×10^6mm/hr
*September 22, 2013*

**Physical Chemistry**

∫ β δT = ∫ 1/V δV Since β independant of T, ∫ β δT = βT + constant. βT = ∫ 1/V δV Use ∫ 1/x dx = ln(x) + constant βT = ln(V) + constant .: V = k e^(βT)
*September 22, 2013*

**Science**

Let u be the horizontal speed and v the vertical. u(0)=8.0m/s, v(0)=0m/s Let x be the horizontal height and y the vertical. x(0)=0m, y(0)=20m y(t) = y(0) + v(0) t -(9.81/2) t^2 Find t when y(t) = 0m So: 0m = 20m - 4.905(m/s^2) t^2
*September 22, 2013*

**Algebra**

If n is the least of the three consecutive odd numbers, the others are: n+2, n+4. So: 5(n) +35 = 2(n+2+n+4) Solve for n, then find 3n+6
*September 22, 2013*

**Math**

A(x+5)+2(−Bx+2) = (A-2B)x+(5A+4) So: (A-2B) = 17 (5A+4) = 219 Solve the second for A, substitute into the first and solve for B, then find A-B.
*September 22, 2013*

**Math**

b + 2c = 859¢ b + 2d = 951¢ b + c + d = ((b + 2c) + (b + 2d))/2
*September 22, 2013*

**Science/ Chemistry**

P: 30.973762(2) O: 15.999(4) Ratio of O to P is: ((0.967-0.422)/0.422)*(30.973762/15.999) = 2.50 The empirical formula is correctly derived from the given masses. The empirical equation also balances.
*September 22, 2013*

**Chemistry**

Three times as many.
*September 22, 2013*

**Discrete Mathematics**

Consider that for any integer (n), (2n+1) is an odd number. By expansion and collecting terms, (2n+1)^2 = ______. Since _______ is an integer it follows that (2n+1)^2 is odd. Therefore the square of any odd number is also an odd number.
*September 22, 2013*

**Discrete Mathematics**

An argument is valid if and only if its conclusion is entailed from its premises, A valid argument is not necessarily sound. That is, the premises do not need to be true. Hence you only need to examine the form of the argument, not the soundness of the premise. The form is as ...
*September 22, 2013*

**Chemistry**

Exchange the acidic proton.
*September 22, 2013*

**Math**

find: a) carlo's speed in the last part of the journey. Carlos travels 16km at 20kph for: 20/16 hours. Thus Carlos travels the remaining (35-16) km for (2-20/16)hours at: (35-16)/(2-20/16)kph. b) the time when Arnold reaches town A. Arnold travels 35km at 25kph for: (35/25...
*September 22, 2013*

**Math**

distance = speed multiplied by time. Measure all distance in kilometres and all time in hours. The car travels: c(t) = 40 t The bus travels: b(t) = 56 (t - 0.5) Solve for t when c(t)=b(t)
*September 22, 2013*

**Math**

Parallel lines have the same gradient. The gradient of the first line is: 4/7 The gradient of the second line is: -9/m Thus: 4/7 = -9/m Solve for: m = ...
*September 22, 2013*

**Math**

2. Profit of n items made and sold is: P(n) = (45.00-30.00)n - 1200.00 a. Find n when P(n)=0 b. Find: -P(400) (Loss is negative profit) c. Find: P(1000)
*September 22, 2013*

**Math**

1. The area of a parallel trapezoid is half of the product of the height and the sum of the lengths of the parallel sides. The height is difference between the projections of A and B on the y-axis. (Ie: 5-2) The length of each side is the difference between the x-axis ...
*September 22, 2013*

**Math**

Let the scores be x, y, z. Solve the three simultaneous equations: x + y + z = 225 x + y = z + 61 x = y + 6 Start by substitution: x=y+6 2 y + z = 219 2 y = z + 55 et cetera...
*September 22, 2013*

**Chemistry**

Use Nt/N0 = e^{-kt} 1[yr] = a = 31557600[s] (1/2) = e^(-kh) Where: Half life: h= 4.5e9 * a = 1.420092E+17[s] k = -ln(0.5)/1.420092E+17 .: k = 4.8810019E-18[/s] Okay, so far. To continue... Assume there is n atoms of U238 in the sample. t=1 second latter there is n-29. (via 29 ...
*September 22, 2013*

**algebra**

The sum is this: X = (1/5 + 1/4 + 1/3 + 1/6)*X + 12 X = (57/60)*X + 12 Simplify and solve for X
*September 22, 2013*

**Algebra**

Ah, I see now. Then it looks all good. The numbers are sorted in increasing order, and a surd is an irrational number.
*September 21, 2013*

**Algebra**

Provide your answer and we'll check it.
*September 21, 2013*

**Chemistry**

[H|D]2O + Cl2 = [H|D]Cl [H|D]Cl + AgNO3 = AgCl + [H|D]NO3 Molar mass H2O: W1 = 18.01532 g/mol Molar mass D2O: W2 = 20.02763 g/mol Molar mass AgCl: W3 = 143.3214 g/mol Sample mass: Ms = 1g Precipitate: Mp = 0.3800g Assay Volume: Vs = 1.00L Aliquot Volume: Va = 25.00mL Let n1 ...
*September 21, 2013*

**algebra**

There is insufficient information. You need to know the angle of the vertix that joins the two given sides. Height: 14*sin(angle) Area: 22*14*sin(angle)
*September 21, 2013*

**algebra**

(fg)(x) is the function that is the multiple of the two functions f and g. (fg)(x) = f(x) * g(x) (fg)(x) = (-6x-1) * (4x^2) ...So then just multiply the terms.
*September 21, 2013*

**algebra**

One way to indicate a subscript in plain text is to use the underscore in the same way the hat indicates a superscript. Like so: {a_n : a_n = 2^n -1} = {0, 1, 3, 7, 15, ...} That is: a_0 = 0 a_1 = 1 a_2 = 3 a_3 = 7 a_4 = 15 ... Using the array notation of most programming ...
*September 21, 2013*

**Math**

Given: point and line. Point: (P, Q) Line: Ax + By = C Since a line perpendicular to the given line will have a gradient of (B/A), and since the equation of a line with that gradient passing through the given point is: (y-Q)=(B/A)(x-P) Just rearrange to required format: y = (B...
*September 21, 2013*

**Math**

100 cm = 1 m
*September 19, 2013*

**Math**

1 g = 1/1000 kg
*September 19, 2013*

**Math help Ms. Sue please**

The answer to 1 and 4 is to rearrange to collect like terms. I suspect _Question_ 4 is wrong. 3x - 2/9 was probably meant to be : (3x-2)/9
*September 19, 2013*

**Math 75%**

Answer 1. is correct Answer 2. is correct Answer 3. is correct Answer 4. is _wrong_
*September 19, 2013*

**Math**

Find the cubic root of 1800.
*September 19, 2013*

**Math**

One advantage of the metric system is that its units of measure scale by multiples of 10. You just have to memorise the prefices. In this case "milli-" means 0.001 times. That is, there are 1000 milligrams to the gram. 1000 mg = 1 g 2000 mg = ___ g
*September 19, 2013*

**math**

Just multiply. Distance equals the product of time and speed. d = t * v
*September 19, 2013*

**physics**

Determine the initial speed. Use the classical mechanics equations. Speed: 0 = u -g t → rearrange to substitute for t into: Displacement: h = ut - (1/2) gt^2 → find u in terms of h and g. Determine the maximum range. Use a 45° trajectory. d = u^2/g → ...
*September 19, 2013*

**science**

______ is composed of ____. A _____ is a unit of matter composed of one or more _____. An _____ is a _______ composed of same kind of _____. A _______ is a ________ composed of two or kinds of ______. A ______ is an arrangement of ______ composed of _____ in a repeating latice.
*September 19, 2013*

**chemistry**

Find the Ksp of KI at 30C. Ksp = [K{+}]*[I{-}] That will determine the mole concentration of dissolved KI. Multiply by volume (in L) and molecular mass to determine the mass. Subtract that from the mass of supersaturated KI to determine the mass of precipitate.
*September 19, 2013*

**chemistry**

Balance the equation C3H8 + _n_ O2 = 3 CO2 + 4 H2O mass(O2) = n * mass(C3H8) * molarmass(O2) / molarmass(C3H8)
*September 19, 2013*

**Calculus (math)**

Begin with: sin(x+y) = sin(x)cos(y) + cos(x)sin(y)
*September 19, 2013*