oobleck

Newest questions and responses by oobleck
  1. Maths

    If the bridge's length is x, then the train's engine has to move (x+100) meters to pull the last car across. So, since distance = speed * time, x+100 = 54000 * 12/3600

    posted on January 16, 2019
  2. Algebra repost

    I like "n>4" for "a number is more than 4" But for "a number more than 4" I like 4+x

    posted on January 16, 2019
  3. Maths

    That's cylindrical, not cylienderI called Anyway, if the wire is of length x cm, then you need the volumes to be equal: 14^2 * 10 = 0.4^2 * x now just find x.

    posted on January 16, 2019
  4. math

    After the first transfer from A, P(B=3stars, 1heart) = 2/3 P(B=2stars, 2hearts) = 1/3 So, the probability of getting a start when drawing from B is 2/3 * 3/4 + 1/3 * 1/2 = 2/3

    posted on January 16, 2019
  5. Math

    maybe. You are correct. But, maybe they wanted M' - everything which is not in M. In that case, (A).

    posted on January 16, 2019
  6. math

    yeah, yeah. OK, that's fair, and I answered it (in terms of how many cards Kai has.) But, unless you start tossing in some actual numbers, don't expect a final numerical answer.

    posted on January 16, 2019
  7. math

    clearly, the answer is 42. But that does not answer your question: how do you get it? Maybe you bounce on your head while spinning on a beach ball Maybe you study some math. Or maybe, just maybe, you ASK A REAL QUESTION!

    posted on January 16, 2019
  8. Mathematics

    8/9 is correct, but 8/9 ≠ 1 1/9 !!! 1 1/9 = 10/9

    posted on January 16, 2019
  9. Math

    If the two angles share a vertex (the middle letter) and one side (an outside letter) then they are adjacent.

    posted on January 16, 2019
  10. Algebra

    There is a total of n*t man-days of labor. That is 56*7 = 392 So, your relationship is nt = 392 or, n = 392/t

    posted on January 15, 2019
  11. Math

    10 3/7 + 18 2/7 That's just 10+18 + 3/7 + 2/7 28 + 5/7 or 28 5/7

    posted on January 15, 2019
  12. Mathematics

    I assume you can draw the Venn diagram. If not google is your friend. If s passed science, then s+15 passed math. So, s + (s+15) - 12 = 60-7 now you can answer questions 2,3 For #4, 60-7 passed something; 12 passed both, so 60-7-12 passed one or the other,

    posted on January 15, 2019
  13. math

    well, the projection of u onto v is (u.v)/|v| Then recall that v = |u|cosθ v/|v| and the orthogonal component of u is |u|sinθ w/|w| where w is orthogonal to v

    posted on January 15, 2019
  14. algebra

    well, -3x+6y cannot be both 10 and -4, right? so, ...

    posted on January 15, 2019
  15. Math

    all you need to work these is to recall that sin(ax) has period 2π/a sin(x-b) has a phase shift of b to the right. so, sin(ax-b) = sin(a(x - b/a)) has period 2π/a and a phase shift of b/a y = f(x)+k has a vertical shift of +k So, 1. y=sin(x+pi/2)

    posted on January 15, 2019
  16. Math

    even multiples of 5 end in 0. So, you want numbers ending in 2 or 4 odd multiples of 5 end in 5, so you want numbers ending in 7 or 9 Now look at the list of even remainders when divided by 7: 1,3,5,8,10,12,15,17,19,22,24,26,29,31,33,36,38,40,43,45,47,...

    posted on January 15, 2019
  17. Math

    google is your friend. You might start here: fac-staff.seattleu.edu/nirmalag/web/mpmathclub/6thMIC2012Cind.pdf

    posted on January 15, 2019
  18. Math

    profit of 47.35-12.85, split 3 ways, right? (divided by 3)

    posted on January 15, 2019
  19. Math

    that would be 16 days, right? 1/√2 * 1/√2 = 1/2

    posted on January 15, 2019
  20. math

    do you mean the area under the line? If so, just draw the line, and you can see that it is ∫[0,2] 4-2x dx

    posted on January 15, 2019
  21. algebra

    for multiplication, just expand out (ab^2 +3ab+8a^2)(-5ab^2) every term in the product will have some combination of powers of a and b, so it will still be a polynomial. same for addition and subtraction

    posted on January 15, 2019
  22. math

    well, the price must be 10+25, or a 250% increase 25 = 10*2.5

    posted on January 15, 2019
  23. Math

    wait. you say that if there are 22 passengers, each ticket costs $60 but if there is one empty seat, each ticket costs $120? and if there are 2 empty seats, each ticket costs $180? I don't think so! But assuming that's so, let's go on, and you can fix it

    posted on January 15, 2019
  24. Calculus

    xy = 800000 If the outer fence costs $c/m, then the inner fence costs $2c/m So, the total fence cost is x(2*c + 2c) + y*c so we want to minimize z = 4x + 2*800000/x dz/dx = 4 - 1600000/x^2 = 4(x^2-400000)/x^2 we want dz/dx=0 for a minimum, so x^2 = 400000

    posted on January 14, 2019
  25. algebra

    w(3w-10) = 8 4*2 = 8 so, the width is 4 ft and the length is 3*4-10 = 2 (strange that the length is less than the width, but oh well...) Now, as it is very easy to find, using google, 1 meter is 3.28 feet, so 1 ft is 1/3.28 meter So, the width is 4/3.28 =

    posted on January 14, 2019
  26. algebra

    check your post of 1:05 pm before reposting, eh?

    posted on January 14, 2019
  27. math

    huh? $96 is 3/4 of her money, right? The coat cost 1/4 of her money, so its price was 1/3 of 96 = $2 or, since she started with $x, 3/4 x = 96 x = 128 The coat cost 128-96 = 32 since 32 is 1/4 of 128

    posted on January 14, 2019
  28. algebra

    you know that area is length * width, right? Since the width is 12 less than twice the length, if the length is x, then the width is 2x-12 So, now you know that (2x-12)(x) = 270 2x^2 - 12x - 270 = 0 x^2 - 6x - 135 = 0 (x-15)(x+9) = 0 x = 15 so, the

    posted on January 14, 2019
  29. Math

    The scale is 4" : 6'1" = 4" : 73" = 4:73 = 1:18.25

    posted on January 14, 2019
  30. math

    to keep these straight, consider a horizontal slope (θ=0°) all the force is perpendicular to the plane, so clearly that component is F*cos0° So, for nonzero θ, the components of F are perpendicular: F cosθ parallel: F sinθ

    posted on January 14, 2019
  31. Geometry

    not incorrect, but we usually try to simplify fractions, such as 3/9 = 1/3 4/1 = 4 etc. However, leaving it as -4/-1 does indicate just how you performed your calculation. I think your teacher (and probably an online answer key) would prefer just 4

    posted on January 14, 2019
  32. math

    recall that for the point (x,y) sinθ = y/r cosθ = x/r tanθ = y/x So, for your two problems, If sinθ=7/13 and cosθ=12/13 find tan θ and cot θ Unfortunately, no angle θ has sinθ=7/13 and cosθ=12/13 since 7^2+12^2 ≠ 13^2 However, 5^2+12^2 = 13^2,

    posted on January 14, 2019
  33. Geometry

    you are correct. Calculate the change in x and the change in y between the two points. The slope is y-change/x-change: (1-5)/(-3-(-2)) = -4/-1 = 4

    posted on January 14, 2019
  34. algebra

    to find x, just equate the two values for y: 3x + 4 = -0.35x - 10 3.35x = -14 x = -4.179 (or, exactly, -1400/335 = -280/67)

    posted on January 14, 2019
  35. math

    #3: the cross-product is the outsides = insides so, ...

    posted on January 14, 2019
  36. maths

    Huh? Of course z lies on a circle! That's kind of vague. If z = x+iy, then (x,y), (y,-x), (1,0) are collinear See what you can do with that.

    posted on January 14, 2019
  37. maths

    (k+w)(k+w^2) = w^3+kw^2+k^2w+k^3 = = (w^4-k^4)/(w-k) See where this takes you: https://www.wolframalpha.com/input/?i=sum(k%3D1..n)+(w%5E4-k%5E4)%2F(w-k)

    posted on January 14, 2019
  38. Chemistry

    that's "presence" not "pressure" Figure how many moles of CaCO3 you have in 25g Now, looking at the reaction equation: CaCO3 + 2HCl = CaCl2 + H2O + CO2 you can see that each mole of CaCO3 produces one mole of CaCl2 ...

    posted on January 14, 2019
  39. math

    yeah, yeah sorry that no one was here to tell you to, I don't know, substitute x=5 into the function? Geez, did you even read what they told you? PS don't forget that p(x) is in millions of $$$$

    posted on January 14, 2019
  40. Math

    If the fast pump can fill it in x hours, then the slow pump takes x+5 hours. So, now you know that 1/x + 1/(x+5) = (1/2)/3 So just find x

    posted on January 14, 2019
  41. Math

    hmmm. They have told you that if the list price is x, then the marked-down prices are D(x) = 0.80 * 0.90 = 0.72x H(x) = 0.75 * 0.85 = 0.6375x See what you can do with that...

    posted on January 14, 2019
  42. math

    yeah, yeah sorry that no one was here to tell you to, I don't know, substitute x=5 into the function? Geez, did you even read what they told you? PS don't forget that p(x) is in millions of $$$$

    posted on January 14, 2019
  43. Trigonometry

    recall that x' = x cosθ - y sinθ y' = x sinθ + y cosθ

    posted on January 14, 2019
  44. math

    A) polynomial (quadratic, to be exact) B) solve -4x^2+20x-9 = 0 using the quadratic formula or factoring or completing the square.

    posted on January 14, 2019
  45. math

    surely you recognize that this is a linear function. So, plot any two points (pick two values of x and calculate y) draw a line between the points and extend it both ways. That is the graph. If still unsure, google "linear function" or, what the heck,

    posted on January 14, 2019
  46. math

    not any type I know not rational, polynomial,etc. whenever you see a function such as y(x) x (inside the parens) is the independent variable, y of x depends on x.

    posted on January 14, 2019
  47. Math

    3^3 = 27 4^3 = 64 so, ...

    posted on January 13, 2019
  48. Chemistry

    8/3 = 2^x * (4/3)^y (4/3)^y = 8/3 * 2^-x y ln 4/3 = ln(8/3) - x ln 2 y = (ln(8/3) - x ln2)/ln(4/3) ≈ (0.9808-0.6931x)/0.2877 = 3.4094 - 2.4094x

    posted on January 13, 2019
  49. Math

    the domain for all rational functions is all reals, except where the denominator is zero. So, the domain here is all reals except x = 16/5 There is a horizontal asymptote at y=0, and there is a vertical asymptote there, positive on one side and negative on

    posted on January 13, 2019
  50. Math

    10m = 1000cm so, there are 4*(1000/20) = 200 plants in all

    posted on January 13, 2019
  51. math

    If he raised the price by x%, then if the cost was c, he sold it for c(1 + x/100) Then, after the 16% discount, his sales price was 5% above cost, so c(1 + x/100) * 0.84 = 1.05c Or, dividing by c, (1 + x/100) * 0.84 = 1.05 x = 25 So, he raised his price by

    posted on January 13, 2019
  52. algebra

    the midpoint is at ((-1+4)/2,(5-3)/2) = (3/2,1)

    posted on January 13, 2019
  53. math

    moving to the right means x is increasing. So, where do you have x'(t) > 0?

    posted on January 13, 2019
  54. calculus

    while y'=1 at x=0, y(x) is discontinuous there. y(0) -> 0 on the left, y(0) = 1 on the right. Do the graph, and you can see that y is not differentiable at x=0 read the definition again.

    posted on January 13, 2019
  55. Calculus

    each rectangle has width (9-1)/4 = 2 using left endpoints, that would mean you want 2(f(1)+f(3)+f(5)+f(7)) = 2(1+9+25+49)

    posted on January 13, 2019
  56. Math

    recall that ln e = 1 so, lnx-1 = 0 when x=1 clearly, when x gets huge, lnx-1 is very close to lnx so the horizontal asymptote is just y = lnx/lnx = 1

    posted on January 12, 2019
  57. Math

    If k=9, (x-3) / (x^2-6x+9) = (x-3)/(x-3)^2 = 1/(x-3) Not sure what you're after, but maybe this will help

    posted on January 12, 2019
  58. Algebra

    Ooops my bad. If you swap first, solve for y you need to review how to find an inverse function. If y = 2x-3 to find f^-1, first swap variables x = 2y-3 then solve for y y = (x+3)/2 Or, you could solve for x and then swap y = 2x-3 y-3 = 2x (y-3)/2 = x x =

    posted on January 12, 2019
  59. Calculus

    what? You cannot evaluate f(x) at x=2 and x=4? The height of the rectangles is f(2) = 2 - cos(2π) = 2-1 = 1 f(4) = 4 - cos(4π) = 4-1 = 3 Since the width of each rectangle is 2, the area a = 2*1 + 2*3 = 8 Now study your text's examples again, and it

    posted on January 12, 2019
  60. Math

    for any x, the slope of the tangent line is h'(x) First, simplify things by noting that e^-lnx = 1/e^lnx = 1/x h'(x) = cos(1/x) * -1/x^2 h'(1/π) = -π^2 cos(π) = π^2

    posted on January 12, 2019
  61. Calculus

    Or, more conventionally (I think) f(x) = ∫[0,x] arctan(t) dt By the 2nd FTC, f'(x) = arctan(x) so, f'(0.5) = arctan(0.5) ≈ 0.46

    posted on January 12, 2019
  62. Algebra

    First, make sure you have typed things correctly. What you have written is gibberish. So, I shall go with g(x) = -4/(-x-3) + 1 First of all, what's with all those - signs? Oh, well ... swap variables and solve for x: h(x) = 4/(x-1) - 3 = (7-3x)/(x-1) By

    posted on January 12, 2019
  63. Calculus

    recall that e^lnx = x. So, e^(2lnx) = (e^lnx)^2 = x^2 So, you just want ∫x^2 + e^(2x) = 1/3 x^3 + 1/2 e^(2x) + C

    posted on January 12, 2019
  64. Calculus

    use two rectangles on [1,5] means they both have width 2. So, the 2 subintervals are [1,3] and [3,5] The midpoints are thus at x=2,4 So, take f(2) and f(4) for the heights. Your approximation is just the sum of those two rectangles.

    posted on January 12, 2019
  65. math

    if each book cost x, then total cost = 16x if each book sold for that same amount, total revenue = 30x 30/16 = 1.875 or 87.5% gain Not sure whether I interpreted your meaning correctly It's kinda vague

    posted on January 12, 2019
  66. Maths

    you just need to think on these a bit. a boy and a girl can be chosen in 5*4=20 ways Once chosen, they count as a single person with 7 others, so there are 20*7! ways to arrange them now use the same logic, deciding how many ways 2 boys/girls can be chosen

    posted on January 12, 2019
  67. Science

    M = moles/liter So, for your solution, 2.0mole/0.4L = 5.0M

    posted on January 12, 2019
  68. Math

    the solution to the system is a point. Not much of a graph. Since the two graphs have different slopes, the two lines must intersect -- in exactly one point.

    posted on January 11, 2019
  69. math

    unless it's equilateral or equiangular it's not regular

    posted on January 11, 2019
  70. Math

    6/5 divided by blank equals 6 or, (6/5)/x = 6 now multiply by x: 6/5 = 6x now multiply by 1/6 6/5 * 1/6 = x 1/5 = x

    posted on January 11, 2019
  71. Math

    looks like you should have been studying instead of waiting for someone to do them for you. Still, maybe what I showed you will help.

    posted on January 11, 2019
  72. Math

    #1 Note that x+3y=4 can be rewritten as 4x=-12y+16 so both lines are the same, so C #2 Y=5x+7 can be written as 3y-15x=21 So, the two lines are parallel: D #3 x-2y=6 is 3x-6y=18 So, it's the same line: C #4 y-7x=-14 is 7y-49x=-98 so, D Looks like you need

    posted on January 11, 2019
  73. math

    just as a general rule, you divide one quantity by another. Suppose you have a product which sells for $52.17 for 9 boxes. The unit rate is $/box, so you divide $52.17/9box = 52.17/9 $/box = $5.80/box or, say you go 23 miles in 3 minutes, and you want your

    posted on January 11, 2019
  74. Math

    why 2 halves?

    posted on January 11, 2019
  75. Physics

    he said to divide the time into 3.0m That is, divide the 3.0m by time, giving m/s

    posted on January 10, 2019
  76. Geometry

    actually, 2+7=9 -5 is 7 units below y=2

    posted on January 10, 2019
  77. math

    not so. I'll show you how to find the answer. Using the formula for the nth term of an AP, you know that a+6d = 2(a+2d) 4/2 (2a+3d) = 16 Now you can find a and d, so you just need to know how many terms there are. If there are k terms, then a+(k-1)d = 72

    posted on January 10, 2019
  78. Probability

    P(A or B) = P(A)+P(B)-P(A and B) = 1/13 + 1/4 - 1/13 * 1/4 = 4/13

    posted on January 10, 2019
  79. Math

    10-x >= 3

    posted on January 10, 2019
  80. Math

    you can do it in a few ways. One way is to see how many small cubes fit in each dimension 1/2 = 6/12 3/4 = 9/12 so, the block can hold 6*6*9 = 324 small cubes Or, 1/2 * 1/2 * 3/4 = 3/16 m^3 scale that by a factor of 12 and the volume scales by a factor of

    posted on January 10, 2019
  81. math

    6.50 each is 6.50/1 right? "each" means the unit rate!

    posted on January 10, 2019
  82. Math

    wow I did mess that up! The derivative is 2cos(x^3) * -sin(x^3) * 3x^2 = -6x^2 cos(x^3) sin(x^3) or, as Reiny put it.

    posted on January 10, 2019
  83. Algebra 2

    substitution: z = -19-2x+3y so use that to get 5x+y-(-19-2x+3y) = -7 -x+6y-(-19-2x+3y) = 35 or 7x-2y = -26 x+3y = 16 Now you have x = 16-3y, so that gives 7(16-3y)-2y = -26 -23y = -138 y = 6 so, x=16-3y = 16-3*6 = -2 so, z = -19-2x+3y = -19-2(-2)+3*6 = 3

    posted on January 10, 2019
  84. math

    well, they must all add up to 360, right? so add up those three and subtract that sum from 360

    posted on January 10, 2019
  85. Algebra

    correct, though it usually called "distributive"

    posted on January 10, 2019
  86. algebra

    well, first, draw the triangle! it is easy to find the area, since the base is a vertical line. Now it should be clear that one inequality is x > 1 Now determine the equations of the other two sides, and decide whether y is above or below each line.

    posted on January 10, 2019
  87. Math

    the limit exists, and it is in fact the derivative

    posted on January 10, 2019
  88. calculus

    using the product rule, dp/dt * v^1.3 + p*1.3 v^0.3 dv/dt = 0 so, I guess you could say that (dp/dt)/(dv/dt) = -1.3p/v or, by rearranging the 1st equation, p = kv^-1.3 dp/dt = -1.3kv^-2.3 dv/dt (dp/dt)/(dv/dt) = -1.3k/v^2.3

    posted on January 10, 2019
  89. Math

    come on sin(π/2) = 1. So, k=π/2 so, f(x) = sin(π/2 x) for x>1 That way the limit on both left and right is f(x) = 1

    posted on January 10, 2019
  90. Math

    the derivative of u^2 is 2u u' the derivative of cos(u) is -sin(u) u' so, with u=x^3, the derivative of cos^2(x^3), using the power rule as well, is 2cos(3x^2) * -sin(3x^2) * 6x

    posted on January 10, 2019
  91. Math

    at x=1, x^2 = 1 so, you need at x=1, sin(k) = 1 so where is sin(k) equal to 1?

    posted on January 10, 2019
  92. math

    if they made only large and medium, then 291-5 = 286 mediums seems kinda lop-sided to me.

    posted on January 10, 2019
  93. algebra

    not sure I know what a "literal equation" is. Care to elaborate?

    posted on January 10, 2019
  94. Math

    clearly, that will be 4 * 1 1/2 = 4 4/2 = 6 gallons

    posted on January 9, 2019
  95. Math

    no figure to look at. Sorry

    posted on January 9, 2019
  96. Math

    except for the lx part, this is just algebra I 3 + ln (4x) = 4 ln(4x) = 1 Now, get rid of the ln by doing its inverse: e^ 4x = e^1 x = e/4

    posted on January 9, 2019
  97. Math

    No idea where angle 4 is, but you need to recall that vertical angles are congruent alternate int/exterior angles are congruent adjacent angles are supplementary etc. Time to review your theorems on parallel lines and their transversals

    posted on January 9, 2019
  98. Math

    A(t) = 497*(1/2)^(t/38) You can see that when t grows by 38, you multiply again by 1/2 now plug in t=4

    posted on January 9, 2019
  99. Technology

    No. Old vacuum-tube machines filled whole rooms The silicon chip enable miniaturization.

    posted on January 9, 2019