Friday

September 30, 2016
Total # Posts: 1,280

**statistics**

there are 11 letters 3 of them occur twice possible arrangements equal ... 11! / (2! * 2! * 2!)

*August 12, 2016*

**Calculus**

velocity is dx/dt integrating gives position t/42 = dx/dt t/42 dt = dx integrating ... t²/84 = x = 100/21

*August 10, 2016*

**math**

there are 9C4 ways of selecting four printers there are 5C4 ways of selecting four good printers the probability is ... 5C4 / 9C4

*August 10, 2016*

**Science**

the simplified range equation is ... Rmax = v² / g ... 100 = v² / g ... 100 g = v² when an object is thrown straight up, the initial kinetic energy becomes gravitational potential energy ... ½ m v² = m g h ... v² / (2 g) = h combining the two ...

*August 8, 2016*

**math**

b + c = 45 / 2.5 = 18 kph b - c = 39 / 3.25 = 12 kph adding equations (to eliminate c) ... 2 b = 30 kph solve for b substitute back to find c

*August 7, 2016*

**chemistry**

a mole contains Avogadro's number of particles 5 moles = 5 * 6.02E23

*August 7, 2016*

**Geometry**

90º - a = (180º - a) / 5 450 - 5a = 180 - a 270 = 4a

*August 7, 2016*

**Algebra/Quadratic Functions**

the minimum lies on the axis of symmetry x min = -b / 2a = -(-200) / 2*2 = 50

*August 7, 2016*

**Calc**

f(x) = x^2+(1000-x)^2 ... = x² + 1E6 - 2000x + x² ... = 2x² - 2000x + 1E6 the minimum is on the axis of symmetry at x=500 ... the function increases from there so as x increases (below x=500), the function decreases f(0) = 0² + (1000 - 0)² = 1000²...

*August 7, 2016*

**Math calculus**

s.a. = 6 s² da/dt = 12 s ds/dt v = s³ ... 8 = 2³

*August 7, 2016*

**Maths**

M = 2R M + 11 + R + 11 + 3 = 75 Roy's dessert ... 11 + 3 = $14 3R + 25 = 75 ... R = 50/3 Roy's meal ... $50/3

*August 7, 2016*

**Science**

f = 1500 * g * .2

*August 6, 2016*

**maths**

4 (1 / 2 μf) = 1 / Ce Ce = 2 μf / 4

*August 6, 2016*

**Math**

d = h cot(32º) d - 8 = h cot(43º) 8 = h [cot(32º) - cot(43º)] h = 8 / [cot(32º) - cot(43º)]

*August 6, 2016*

**Math**

3/5 = 6/10 ... so there were 6 groups of boys the 2/5 of the class that were girls resulted in 2 groups of 1/5 each an aside ... the girls' groups were twice as large as the boys' groups

*August 5, 2016*

**physics**

don't know if significant figures are an issue but there are two in the data, and four in the result

*August 5, 2016*

**Science**

the horizontal velocity is the total velocity multiplied by cos(30º) at the topmost point, there is no vertical velocity ... so the K.E. is ... E cos²(30º)

*August 4, 2016*

**Algebra**

nancy starts with $50 more, but annie can save $5 more per week 50 / 5 = 10 weeks

*August 4, 2016*

**physics**

h = ½ g t² + 30 t = -4.9 t² + 30 t substitute 20 for h to find the time ... use the quadratic formula the time of max h is on the axis of symmetry of the parabola ... t = -b / 2a = -30 / -9.8 ... plug in the time to find h max the velocity is zero at max h the...

*August 4, 2016*

**physics**

average velocity = distance / time = 42 m / 2 s = 21 m/s average velocity = (initial + current) / 2 gravity slowed the arrow for 2 sec ... current = initial - (2 * 9.8) (Vi + Vi - 19.6) / 2 = 21 m/s solve for Vi time up = time down flight time = 2 (Vi / g)

*August 4, 2016*

**Math**

5 pies means 20 quarters (5*4) 3 quarters per neighbor means 6 neighbors, with two quarters left over 3*6 = 18 ... 18 + 2 = 20

*August 4, 2016*

**I need help - precalc**

1/√3 is the tangent of 30º or π/6 ... this is the reference angle -1/√3 is the tangent of the reference angle in quadrants II and IV so the x-values are ... 5π/6, 11π/6, and 17π/6

*August 4, 2016*

**Math**

no it is three decimal places to the right, so it is one thousandth the value of the 1st five (10^-3)

*August 4, 2016*

**math**

you could say "a" percent is like "a" peanut...one it doesn't use the term "percentage" regardless, the question is not well worded (1.01 n) * .20 = 400

*August 4, 2016*

**biology**

the high specific heat will help keep the pond from becoming a "fish stew"

*August 4, 2016*

**Biochemistry**

pOH = 14 - pH = 2.5 [OH⁻] = 1.0E-2.5 = .0032 M 1.75 * .0032 = .0056 moles of KOH multiply by the molar mass to find the quantity required

*August 3, 2016*

**chemistry**

.250 L of a .1 M solution contains .025 moles of solute mass needed is ... .025 * 204.23 g

*August 3, 2016*

**Chemistry**

in general; the lower the elevation, the higher the atmospheric pressure but the pressure (barometric) varies with weather conditions B might be the best answer for this somewhat ambiguous question

*August 3, 2016*

**math order of operations**

PEMDAS parentheses, exponents, multiplication, division, addition, subtraction 2*2*3 = 12 12/12 = 1 10 - 1 = 9 9*7 = 63 10 + 63 = 73

*August 3, 2016*

**Chemistry**

volume is inversely related to pressure (Boyle's Law) P1*V1 = P2*V2 108 * 8 = 224 * V2

*August 3, 2016*

**math**

it's in two steps 700 is the start of the 1st step, 7.5% for 6 years ... the result becomes the start of the 2nd step, 8.25% for 4 years

*August 3, 2016*

**Physics**

the horizontal pulling force is ... 260 cos(30º) the vertical pulling force is ... 260 sin(30º) the coefficient of sliding friction is ... [260 cos(30º)] / ... {450 - [260 sin(30º)]}

*August 3, 2016*

**Math**

it could be a looong summer... there are an infinite number of solutions if n and m are the numbers ... n - m = 3¼ , or , n = m + 3¼ m can be ANY mixed number

*August 2, 2016*

**statistics**

2.15 is .85 below the mean this is .85/.5 s.d. (1.7) use a z-score table to find the fraction of the population in this range about .045

*August 2, 2016*

**I need help please - Pre-Calc**

1/√2 is the cosine of 45º (π/4) ... that is the reference angle -1/√2 is the cosine of ... ±3π/4 ... add or subtract multiples of 8π/4 to find the values on the interval x values...-13π/4, -11π/4, -5π/4, -3π/4, 3π...

*August 2, 2016*

**Physics**

a = f / m a = [108.1 - (10 * g)] / 10

*August 2, 2016*

**Physics**

f = m a f = 3 kg * (25 m/s / .10 s)

*August 2, 2016*

**Math**

4 - $2 1 - $5 1 - $10 1 - $50

*August 2, 2016*

**Chemistry**

the molar mass of silver chloride is 143.32 g the molar mass of silver is 107.87 g so the mass of silver in the processed sample is ... .2865 * 107.87 / 143.32 the processed mass divided by the original sample mass is the purity of the original sample

*August 2, 2016*

**science**

zero

*August 1, 2016*

**physics**

a boy uses a slingshot to launch a rock with a velocity of 30m/s how long does it take it to reach a height of 20m,what maximum height does the rock reach, what is the velocity of the rock at this height, what is the velocity of the rock just before it lands

*August 1, 2016*

**physics**

the required takeoff speed for a large airplane is 180mi/hr(80m/s)the plane is capable of accelerating at a rate of 4m/s^2 assume the plane starts at rest, determine the minimum runway length required for this plane to safely take off, a smaller airplane requires a takeoff ...

*August 1, 2016*

**math**

a. v = x (8 - 2x) (15 - 2x) b. x must be less than 4 (the point where the 2nd factor goes to zero)

*July 30, 2016*

**Chem**

CaS ... calcium sulfide

*July 30, 2016*

**Chem**

increasing the temperature (adding energy), will drive the reaction to the left

*July 30, 2016*

**math**

AC ... y = -2 x + 20 BD ... y = 1/2 x D (8,4) BD = √(64 + 16) AD = √(9 + 36) area ABD = ½ √(80 * 45) = 30 area ABEF = 10² = 100

*July 30, 2016*

**math**

a graphical solution seems the most straight forward B(0,0) C(10,0) E(10,10) A(5,10) F(0,10) find the equation for AC, and then the equation for BD D is the intersection of the lines calculate the lengths of BD and AD to find the area of ABD

*July 30, 2016*

**statistics**

the failure rate is 15% the probability of both bulbs being bad is ... .15 * .15

*July 29, 2016*

**Chemistry**

C₃H₈ + 5 O₂ --> 3 CO₂ + 4 H₂O 4 moles of C₃H₈ would normally produce 12 moles of CO₂ ... but there is insufficient O₂ the O₂ is 1/5 of what is necessary, so the yield will be ... 1/5 * 12 moles

*July 29, 2016*

**Science**

the Earth completes one revolution in 24 hr so, how long is the 40th parallel? the "rotational" radius is equal to the radius of the Earth times cos(40º) the length of the parallel (circumference) is 2π times the radius divide the circumference by 24 hr to ...

*July 29, 2016*

**math**

Steve is referring to the 5-12-13 Pythagorean triple

*July 28, 2016*

**math**

S * L = 60 S² + L² = (S + 8)² S² + (60 / S)² = (S + 8)² S² + (3600 / S²) = (S + 8)² S⁴ + 3600 = S⁴ + 16 S³ + 64 S² S³ + 4 S² - 225 = 0 S = 5

*July 28, 2016*

**Chemistry**

1.2E24 / 6.0E23 = 2.0 moles 4.0 moles are added

*July 28, 2016*

**Chemistry**

there are 6.0 x 1E23 molecules in a mole 2.0 moles + 4.0 moles

*July 28, 2016*

**math**

d / r = t 240 / (b + 20) = 180 / b 240 b = 180 b + 3600

*July 28, 2016*

**maths**

1/2 of 1/6 is 1/12

*July 27, 2016*

**pre cal**

the 5th order term is the driver it is an odd power, so the function will have the same sign as x

*July 27, 2016*

**Algebra 2**

it would be infinite

*July 27, 2016*

**@ Ms. Sue**

the key here is "modern" humans (like us) Isaiah is using 6 million in some population growth scenario and getting weird results he's not interested in the start of the genus homo, he want to count people

*July 27, 2016*

**Science**

"modern" humans (us) arrived on the scene about 30 - 50 thousand years ago around the end of the last ice age there was limited interbreeding with the Neanderthals -- who were on the way out there have NOT been people like us around for 6 million years plug a ...

*July 27, 2016*

**someone please help me. - Precalc**

tan(90º - Θ) = cotan(Θ) cotan(Θ) = cos(Θ) / sin(Θ) [cos(Θ) / sin(Θ)] * sin(Θ) = cos(Θ)

*July 27, 2016*

**Math**

x (.20) + (300 - x)(.40) = 300 (.28) .2 x + 120 - .4 x = 84

*July 27, 2016*

**physics**

the rock reaches its peak after 12/g s it ascends at an average rate of ... (12 m/s + 0 m/s) / 2 it then free falls from h m g h = ½ m v² ... v = √(2 g h) t = 2 h / v

*July 27, 2016*

**Physics**

a * [1 - (p / density of Hg)]

*July 27, 2016*

**algebra**

(s + 7)² = s² + 189 s² + 14 s + 49 = s² + 189 14 s = 140

*July 27, 2016*

**maths**

h(x) = 2 - x g(x) = x²

*July 27, 2016*

**maths**

f(x) = g[h(x)] g(x) = x³ h(x) = 2x + 1

*July 27, 2016*

**Physics**

the energy stored in the spring is ... ½ k x² ... this energy is K.E. when the spring is in the neutral position (the middle of its travel) K.E. = ½ m v² ... so the velocity and the amplitude are directly related to each other (both squared) a) velocity...

*July 27, 2016*

**Math**

a) h / 300 = tan(16º) ... h = 300 * tan(16º) b) tan(Θ) = h / (300 - 75)

*July 27, 2016*

**geometry**

the 3rd side must be greater than the difference, and less than the sum, of the 1st two sides

*July 26, 2016*

**Math**

[(8 * 60) + 37] * 25 ft

*July 26, 2016*

**physics**

the average velocity is ... 36 m / 2 s = 18 m/s gravity has slowed decelerated) the arrow by ... 9.8 m/s² * 2 s = 19.6 m/s [v + (v - 19.6)] / 2 = 18 ... v = 27.8 m/s (launch velocity) time to peak is ... 27.8 m/s / 9.8 m/s² peak height is ... time to peak * 27.8 / 2 ...

*July 26, 2016*

**Geometry**

after translation ... [(-6 + 3),(-4 + 5)] = (-3,1) after rotation ... (1,3)

*July 26, 2016*

**Maths**

B = 3 J ... J = B/3 B = J + 450 ... B = B/3 + 450 ... 2B/3 = 450 ... B = 450 * 3/2

*July 26, 2016*

**Statistics**

15 is 1.5 above the mean ... this is 1.5/7.3 standard deviations ... .2055 use a z-score table to determine the fraction of the population this represents 15 yr or less ... 58%

*July 26, 2016*

**engineering mechanics**

normal ... m g cos(30º) parallel ... m g sin(30º)

*July 26, 2016*

**math**

1/A + 1/B = 1/8 ... 15/B = 15/8 - 15/A 6/A + 15/B = 1 ... 6/A - 15/A + 15/8 = 8/8 ... -9/A = -7/8 ... -72 = -7A

*July 26, 2016*

**Math**

x (25 - 2x) (32 - 2x) = 1575 expand the cubic equation find a solver online (use google)

*July 25, 2016*

**physics**

10 min = 600 s 600 s (20 m/s + 30 m/s) = 30 km ave spd = 30 km / 20 min = 1.5 km/min 10 km / 20 m/s = 500 s 10 km / 30 m/s = 1000/3 s 20 km / (1500/3 s + 1000/3 s) = ... 60 / 2500 km/s = 36/25 km/min = ... 1.44 km/min

*July 25, 2016*

**CHECK MY ALGEBRA 2**

?????

*July 25, 2016*

**CHECK MY ALGEBRA 2**

a hole is a disruption at a single point ... try [(x - 4) / (x - 4)] ... the division by zero causes the discontinuity, but the equal numerator means no other point is affected f(x) = (x - 4) / [(x - 4) (x + 2)]

*July 25, 2016*

**Physics**

assumptions ... the person does not ride the ice down ... the height of the break is even with the top of the slope the gravitational potential energy of the ice is converted to kinetic energy and then heat by friction the total energy dissipated is ... m g h = 100 kg * g * ...

*July 25, 2016*

**College physics**

this is the Doppler effect (google it) the pitch (frequency) is higher because you are moving toward the source f = [343 / (343 - 5)] * 4000

*July 25, 2016*

**Physics**

Vh = 3 m/s² * 30 s = 90 m/s ½ m Vv² = m g h ... Vv = √(2 g h) = √( 2 * 10 * 80) tan(Θ) = Vv / Vh

*July 25, 2016*

**chemistry**

pH = 14 - pOH pOH = - log[OH⁻] = - -8 = 8

*July 24, 2016*

**Math**

top area???

*July 24, 2016*

**PHYSICS**

acceleration ... d = 30 s * [(20 m/s + 0 m/s) / 2] cruise ... d = 15 s * 20 m/s deceleration ... d = 5 s * [(20 m/s + 0 m/s) / 2] add the three distances

*July 24, 2016*

**math: permutations**

couple in 1st row ... 2 ways for 1st row ... 4! ways for 2nd row couple in 2nd row ... 4*5 ways for 1st row ... 4! ways for 2nd row [(4 * 5) + 2] * 4!

*July 24, 2016*

**math:age**

2 s = u 3 (s - 9) = u 3 s - 27 = 2 s

*July 23, 2016*

**Help me anyone - Pre-Calc**

Θ is in radians 20º = (2 π / 18) rad 2340 = ½ (2 π / 18) r² 18 * 2340 / π = r²

*July 23, 2016*

**math**

e = p + 50 time = distance / rate ... 1.6 (1800 / e) = 1800 / p substituting ... 1.6 [1800 / (p + 50)] = 1800 / p solve for p, then substitute back to find e and the times

*July 23, 2016*

**Calculus - Differentials**

the error (in D) is ±.05 A = π D² dA = 2 π D dD = .6 π same difference...

*July 23, 2016*

**Calculus**

h = height up wall d = distance from wall by Pythagoras... h² + d² = 20² differentiating ... 2 h dh/dt + 2 d dd/dt = 0 substituting ... (2 * h * -3) + (2 * d * 4) = 0 ... 8 d = 6 h ... d = ¾ h h² + (¾ h)² = 400 solve for h substitute back...

*July 23, 2016*

**physics**

[16 * cos(20º)] / 4.9 the values in the problem are to 2 significant figures ... not sure about hundredths accuracy

*July 21, 2016*

**Science **

I can be traced back to 3000bc, often go unnoticed, can be overhead, under feet or somewhere in between, evolution has changed me, am lighter than I used to be, and can protect your investment.

*July 21, 2016*

**Physics**

distance = 70 * 5 = 350 km speed = distance / time = 350 / (5 + 2)

*July 21, 2016*

**Math**

3, 5, 9, 15

*July 20, 2016*

**Physics**

N is to the left google "right hand SOLENOID rule"

*July 20, 2016*

**chemistry**

(3 / 2) * 41.0

*July 20, 2016*

**Math**

if r = -2, then the denominator is zero...a big no-no factor the numerator and go with B

*July 20, 2016*