Friday

April 18, 2014

April 18, 2014

Total # Posts: 21,761

**Math**

since the new radius is 3/4 the old one, the new volume is (3/4)^3 the old volume (3/4)^3 * 1920 = 27/64 * 1920 = 810

**math**

think of the hexagon as six equilateral triangles. I assume that you can find the area of such a triangle of side 2 (1/6 the perimeter of the hexagon). Now multiply that area by 6, for the six triangles.

**math**

the cow grazes grass in a sector of a circle. The area of a sector of radius r and angle θ is a = 1/2 r^2 θ where θ is in radians, not degrees. So, here we have a = 1/2 (15^2) (24/180 * pi) = 15 pi

**math**

what is 8% more than c? That should equal 162.

**math (cant figure it out)**

TV+HW = 8% + 13% = 21% 21% of 24 hours is .21 * 24 = 5.04 hours

**math**

how many tiles satisfy each category? pick the one with the highest number of matching tiles (should be more than half the tiles, to make it "likely")

**Math**

no maximum amount. That depends on the pressure. Helium may be added to the ball until its skin ruptures. However, the volume of the ball is 4/3 pi * 12^3 in^3

**Math**

only 2 yellow out of 18 marbles. So, P(~yellow) = 16/18

**Algebra**

put it all over (x+4) and you have (8(x+4) + (x-1))/(x+4) = (9x+31)/(x+4)

**Math**

Assuming that both pizzas are cut into the same number of slices, they must have a multiple of 4 slices each, since we can assume that 1/4 a pizza is a whole number of slices. If the pizzas had 4 slices each, then Jim had 3 and Kate had 1. If there were 8 slices, Jim had 3 and...

**MATH**

for a better graph, substitute (24-2x)

**Please help**

what's with the + sign in the integral? ∫ u^3(√u + u^(1/5)) du = e^(7/2) + u^(16/5) du those are just normal power problems.

**Calc Help**

∫ -8e^x - 6sec^2 x dx = -8e^x - 6tan x + C by this point in the course, these should be easily recognized as standard forms.

**Calc**

∫[√x,1] s^2/(1+3s^4) ds Are you sure there's no typo here? As you can see here http://www.wolframalpha.com/input/?i=%E2%88%ABs^2%2F%281%2B3s^4%29+ds this is not an integral I'd expect to find. If you meant ∫[√x,1] s^3/(1+3s^4) ds then it's a...

**Calculus2**

f"(x) = 8x + 4sinx f'(x) = 4x^2 - 4cosx + C since f'(0) = 2, -4+C = 2 C = 6 and f'(x) = 4x^2 - 4cosx + 6 f(x) = 4/3 x^3 + 6x - 4sinx + C since f(0) = 3, C=3, and f(x) = 4/3 x^3 - 14x + 3 - 4sinx

**math**

revenue is price * sales, so (1.3p)(1-x)s = ps(1-.09) x = 30%

**math**

19.8km = 19800m 63cm = .63m 19800m / (22/7 * .63m) = 10,000 revs

**calculus**

when the man is x from the pole, and his shadow is s, 150/300 = h/(250+300) so, the pole's height is h=275 cm so, at any time, 150/s = 275/(x+s) or, more easily manipulated, (x+s)/275 = s/150 x/275 = s/330 x = 5/6 s so, at any time dx/dt = 5/6 ds/dt since dx/dt = 15, ds/dt...

**Precalculus**

look again. It's the same.

**Precalculus**

see http://www.jiskha.com/display.cgi?id=1397673993

**mathes**

ummm, use a calculator? If you want to keep in fraction form, divide out common factors in the top and bottom: 55/3500 = 5*11 / 5*700 = 11/700

**Math**

well, just evaluate 15*14*13 / 1*2*3

**engineering mathematics 1**

you have 2x+y=80 and you want the maximum area, a = xy = x(80-2x) find the vertex of that parabola for max area. You will find that the fence is equally distributed among the lengths and widths. That is, 2x = 40 y = 40 so the max area pen is 20x40

**math**

the quotient is always less than the dividend

**Math**

subtract and you have 7y = -14 y = -2 now plug that into either equation to find x = -3

**Math**

working all those words into numbers, we have maximize m+r subject to 10m + 15r <= 500 25m + 15r <= 600 I see that we have 15m <= 100 so m <= 6 Given that, if we choose only 1 mouse, we have 15r <= 490 15r <= 575 so, r <= 32 max achieved at 6 mice and 29 r...

**Algebra**

If using x lbs of 4% milk, .04x + .30(200-x) = .08(200)

**math**

what, you have no idea how to list multiples of 4? How about I illustrate with multiples of 3? 3,6,9,...

**Math**

the value of the coffee in each part must add up to the whole. So, 7.50x + 9.50(12-x) = 8.00(12) x = 9 so, 9 lbs at $7.50 and 3 lbs at $9.50

**Algebra**

cross multiply to clear the fractions and you have (x+12)(x+8) = x(x+4) x^2+20x+96 = x^2+4x 16x = -96 x = -6

**:-)**

Yeah, I sometimes have to step back and ask myself what it would take for the problem to make sense. It's not always possible to come up with an answer, either!

**Math 4**

It lowered the temp by 27°, not to. 19 - 27 = -8

**Math 3**

From the context, I gather the day temp is 107° and the night temp is -153°. 107 - (-153) = 310° warmer by day than by night.

**Math 2**

or, more generally, 124 - (-21) = ? If a < b, the difference between a and b is b-a.

**Math 221**

The given line has slope -3 So, the parallel line also has that slope. Now you have a point and a line, so the equation is y-5 = -3(x+1) y = -3x+2 Your first line was okay, but then you started dropping x's along the way. x1 = -1, not 1.

**math**

yes, it's 1/5 for each marble. So, the chance of getting BOTH greens is 1/5 * 1/5 = 1/25

**math**

2 greens out of 10 marbles, so: (B)

**math**

(60-25.5)/2 = 17.25

**Calc**

same as last time, only use the quotient rule: g = 5x/f, so g' = (5f-5x*f')/f^2 g'(3) = (5*4-15*3)/4^2 = -25/16

**Calculus**

g' = 8f + 8x * f' g'(3) = 8f(3) + 24*f'(3) = 8*4 + 24*5 = 152

**Math**

Did you try using h(t) = -16t^2 + 128t ???

**Math**

(a) correct. (b) correct (c) correct (d) max height is at t=4. But the question was, what is that height? h(4) = 256 No idea how to graph it with your calculator. The graph can be seen at http://www.wolframalpha.com/input/?i=-16t^2%2B128t

**Algebra**

If he intended to buy x dozen, the price was evidently 210/x cents/dozen. Instead, (x-1/2)(210/x + 3) = 209 x = 6 So, the price per dozen was expected to be $.35 Instead, he wound up paying $.38/doz, meaning he bought 5 1/2 dozen, which cost $2.09

**Physics**

(1500cm^3)/(1.0s) / (pi*(.49/2)^2 cm^2) = 7954 cm/s or 7.9 m/s not sure on B.

**Math (2 Questions) - Please Help**

F+V-E = 2 If you count all the vertices of each polygon, each vertex is counted twice. So, 12+20 + (5*12+6*20)/2 - E = 2 E = 120 draw a diagram. If you draw horizontal and vertical lines through the point and through the center of the circle, you will see that (r-25)^2 + (r-18...

**Algebra**

the function is undefined when you try to divide by zero. So, if b+4=0, the function is undefined.

**Math- urgent**

the obvious one is -265:100 also 53 : -20

**gg**

that would be 125000(.27) = $33,750

**Math**

solve for t in 6 + 31t - 16t^2 = 4 t = 2

**Trig**

use law of cosines. 70^2 = 65^2 + 90^2 - 2(65)(90)cosθ

**college math**

Sounds like they are repeatedly doing surveys. In most of the surveys (19/20), they sample enough of the population to be confident that their results are within 3.2% of the true percentage.

**CALCULUS**

with a slight change to the numbers, this question is treated at http://www.jiskha.com/display.cgi?id=1392927547

**Algebra**

not sure what you want to do. If you just want to do long division, visit calc101.com and click on the "long division" button. Enter your polynomials and see all the details.

**5TH GRADE MATH**

If you mean that the sum of the three perimeters is 140 yards, then you can divide 140 up any way you like. If you pick, say, 30,50,60 yards as your three perimeters, then you can divide the values up as you will. For example perimeter 30: 7x8 yards perimeter 50: 25 ft by 50 f...

**Mathematics**

P is in QI, so if cosP = 5/13, tanP=12/5 Q is in QIII, so if tanQ = 8/15, sinQ = -8/17 17tanPsinQ = 17(12/5)(-8/17) = -96/5

**trigonometry**

h/63 = sin 45

**calculus help**

There's a nice discussion here: http://math.stackexchange.com/questions/126755/lhospitals-rule-with-indeterminate-powers

**Math**

to figure a percentage, just divide and multiply by 100. 2023.60/55953.77 = 0.0361 = 3.61%

**Calculus Help!!!!!**

should be no problem. That's just Algebra II. Anyway, y = x^3/(x+1)^2 y' = x^2(x+3)/(x+1)^3 y" = 6x/(x+1)^4 see the graph and some analysis here: http://www.wolframalpha.com/input/?i=x^3%2F%28x%2B1%29^2

**Precalculus**

tan does not become 2tan expand (a+b-1)^2 and you will see the 2's, just as (a+b)^2 = a^2 + 2ab + b^2

**Precalculus**

You have (tan+sec-1)/(tan-(sec-1)) multiply top and bottom by tan+sec-1 and you have (tan+sec-1)^2/(tan^2-(sec-1)^2) tan^2+sec^2+1+2tan*sec-2tan-2sec)/(tan^2-sec^2+2sec-1) (sec^2+tan*sec-tan-sec)/(sec-1) (tan+sec)(sec-1)/(sec-1) tan+sec

**Calculus Help Please!!!**

As mentioned, let BC = x distance over water: √(x^2+49) distance over land: 11-x (a) energy expended: y = 1.3√(x^2+49) + 11-x dy/dx = 1.3x/√(x^2+49) - 1 y'=0 at x = 70/√69 what do you get for the other parts?

**algebra**

you just have a right triangle with legs 5 and 8. So, the rope, forming the hypotenuse is √(25+64) = √89

**Calc 2**

and the (-2/3)^k part is just a geometric series S = (-2/3)/(1+2/3) = -2/5

**geometry**

x^2 + 6371^2 = (6371+353)^2 x = 2150

**Algebra**

2 hours

**Math**

√(25^2 + 10^2)

**math**

(P2-P1)/P1 * 100

**Calc**

dQ/dt = kQ (if you please)

**CHEM**

since PV/T is constant, if P is held constant, then V/T is constant. if T is increased by a factor of 296/90, then V is increased by a factor of 296/90. So, multiply 3.3 by that factor.

**math (Matrix algebra)**

Enter your data at http://www.gregthatcher.com/Mathematics/GaussJordan.aspx to see all the details

**math (Matrix algebra)**

assuming you mean a determinant, and calling your matrix M, I get |M| = 31-3x So, if 31-3x = 25, x=2 The inverse can be seen at http://www.wolframalpha.com/input/?i=inverse+{{-2%2C+1%2C+x%2B2}%2C{3%2C+x-4%2C+5}%2C{0%2C+1%2C+3}}+ substitute in x=2 if you just want the numbers.

**maths**

since one line is slanting, and the other is horizontal, I'd say they are not parallel. Even is there's an x missing from the 2nd line, it will still not be parallel.

**maths**

x y -4 13/2 -3 5 -2 7/2 ...

**Algebra**

since time = distance/speed, we have 5/x + 5/(2x) = 15/(2x)

**Math**

5% growth is just 1200000*1.05^n after n years for #c, we have 1200000*(1.05)^7*(0.92)^8 = 866,581

**Algebra**

x^2+8x+15 = (x+3)(x+5) so, you have (x+3)(x+5)/(x-4) * (x-4)(x+4)/2(x+3) the x+3 and x-4 cancel, leaving (x+5)(x+4)/2

**math**

out of 36 possible rolls, only 4 have the sum < 5: 12 13 21 22 What's the chance of no 6's? 5/6 * 5/6 so, take 1-P(~6,~6) = 11/36

**Algebra**

the point of Reiny's question is to remind you that division by zero is undefined. So, when b+4=0, the expression cannot be evaluated. That is, when b = -4, the expression is undefined.

**Math**

I get zero. ∫[-1,2] 1-x^2 dx = x - x^3/3 [-1,2] = (2 - 8/3) - (-1 + 1/3) = 0 yeah, I know, we have to divide by 3 ...

**Trig - heh**

now, just change all those 225's to 255's and redo the calculations.

**Math**

PR/QR = sin(Q) PR/120 = sin(10.5)

**Calculus Help Please Urgent!!!**

1/3 pi r^2 h = 30, so h = 90/(pi r^2) surface area = 2 pi r s where r^2+h^2 = s^2, so a = 2 pi r √(r^2 + (90/(pi r^2))^2) = 2/r √(pi^2 r^6 + 8100) for minimum paper, we need da/dr = 0, so, as wolframalpha so ably shows at http://www.wolframalpha.com/input/?i=2+pi+r...

**mathematics for management**

5^x 25^2y = 1 5^x 5^4y = 1 5^(x+4y) = 1 x+4y = 0 3^5x 9^y = 1/9 3^5x 2^2y = 3^-2 5x+2y = -2 x = -4/9 y = 1/9

**math**

Assuming you mean (8^y)^y, we have 8^y^2 = 2^3y^2 1/32^y = 2^-5y 4 = 2^2 3y^2-5y = 2 y = 2 or -1/3

**mathematics for management**

2log(a+b) = log (a+b)^2 = log (a^2+2ab+b^2) 2log a + log(1 + 2b/a + b^2/a^2) = log (a^2 (a^2+2ab+b^2)/a^2) looks the same to me

**math**

Assuming a 360-day year, 8000 * .095 * 1/3 = 253.33

**math**

ignoring all those trailing zeros, 58/6 = 9.67

**calculus**

1/10 ∫[0,10] 3/(x+1) dx = 3/10 ln(11)

**math**

the bisector BD and half the chord CD form a right triangle with the radius BC BC^2 = 3^2+5^2

**math**

the one with an x term, but no higher powers.

**calculus**

So, the height is 40/x^2 c(x) = 2x^2*5 + 4x(40/x^2)*2 = 10x^2 + 320/x set the derivative to zero, and you find minimum cost at x = 2∛2

**Precalculus**

for #2c, there is a second point at about (-1.38,3) see the graph at http://www.wolframalpha.com/input/?i=solve+5x^3-3x^5%2B1+%3D+3

**cal**

false. These are formulas for interest compounded k times per year.

**math**

have you tried your calculator?

**Math**

850000(1+.06/4)^(4*3.5)/4.75 = 220,419 850000(1+.06/4)^(4*5)/5.10 = 224,476

**statistics**

well, who has a negative z score?

**Math**

As I showed you earlier, it is ∫[0,8] 7/(x+1) dx ---------------------- (8-0) = 1/8 (7log(x+1) [0,8]) = 7/8 (log9-log1) = 7/8 log9 what were your solution steps?

**Algebra**

(r+2)/(r+4) - 3/(r+1) = (r^2-10)/(r^2+5r+4)

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