Posts by Scott

Total # Posts: 4,107

  1. statistics

    46 is 3 standard deviations below the mean
  2. math

    like the 1st question , only different numbers use the same technique term value = 1st term + [difference * (term number - 1)]
  3. math

    the difference between consecutive terms is 4 106 = 2 + [4 * (n-1)] ... solve for n , the term number
  4. physics

    find the velocity in m/s ... 36 km/h ---> ? m/s crossing starts when the front of the train enters the bridge ... it finishes when the end of the train leaves the bridge how far does the "whole" train have to move?
  5. physics

    find the velocity in m/s ... 36 km/h ---> ? m/s crossing starts when the front of the train enters the bridge ... it finishes when the end of the train leaves the bridge how far does the "whole" train have to move?
  6. Physics

    oops ... decimal error ... should be ... 6.0 ± 1.7% sorry
  7. Physics

    when quantities are multiplied , percent errors are added (6.0 ± .17%) * (4.0 ± 5%) = ?
  8. Math

    "Females outnumber males by 200, so there are 800 females and 400 males" ... does that look correct? maybe 700 and 500?
  9. Physics

    her legs are of equal length ... so the vertical force components at each foot must be ... 520N / 2 the total force is ... F / .9 = (520 / 2) / .44
  10. Physics

    let ? be the angle ... n is the normal force of the box against the hill ... ? is the coefficient of static friction n = m g cos(?) frictional force parallel to the slope = ? n = ? m g cos(?) gravitational force parallel to the slope = m g sin(?) when the gravitational force ...
  11. Chemistry

    find the mole weights x + 2y = 100 3x + 2y = 180 solve the system for x and y
  12. Math probability

    the z-score is the number of standard deviations (?'s) that a value lies from the mean the z-score table gives the probability of a score's position in a normal distribution eg. the table gives the mean (z-score, zero) a probability of .5 ... half of the population ...
  13. math-distinguishability

    library - out ... 5 - 1 , 4 - 2 , 3 - 3 , 2 - 4 , 1 - 5
  14. Math

    solve the system of equations for x, y, and z those are the coordinates of the point of intersection
  15. science

    the Earth rotates on its axis and revolves around the Sun
  16. math

    what you say you know is incorrect all 52 cards in a deck are different
  17. Maths

    you have two sides of a right triangle ... the distance is the hypotenuse a^2 + b^2 = c^2
  18. Math

    28% off means that the sale price is 72% of the regular price ... 100% - 28% = 72% .72 * p = $666.00
  19. Physics

    the horizontal velocity is constant regardless of height ... the vertical velocity changes due to gravity horizontal velocity = 15 m/s * cos(45º)
  20. Chemistry

    CH3CO2H ? CH3CO2? + H+ [CH3CO2?] [H+] / [CH3CO2H] = 1.8E-5 x^2 / (.25 - x) = 1.8E-5 ... x^2 + 1.8E-5 x - 4.5E-6 = 0 ... x = 2.11E-3 log(2.11E-3) = 2.67 ... good choice
  21. maths

    google 7 digit primes ... it's a long list
  22. Math

    probability of miss ... 1 - 3/4 = 1/4 probability of two misses in a row ... 1/4 * 1/4 = ?
  23. Math

    ... like 16 and 7 ...
  24. Math

    radical 16 ... ?16 ... equals ±4 ... a rational number the product of two rational numbers is rational
  25. Chemistry

    right
  26. Chemistry

    [F]^2 / ([C] [A]^2)
  27. math

    you're going to subtract 4 from x ... and the result is greater than zero keep thinking
  28. math

    you can draw two right triangles ... her line of sight to the top and the bottom are along the hypotenuse x = 40 tan(42º) ... y = 40 tan(32º) ...x + y = height of tower
  29. algebra

    5 * 54 = x * 45
  30. Math

    find the common denominator 8/20 f + 5/20 f + (3/7 * 7/20 f) + 168 = f solve for f , 1/4 f was sold to students
  31. Math

    40000 * [1 + (.025 * 12)]
  32. Math

    adding 7 , then subtracting 5 look at two sets of every other term ... 3 - 5 - 7 - 9 - ... - 10 - 12 - 14 - 16
  33. Math

    xmax is on the axis of symmetry of the parabola -b / 2a = -800 / (2 * -3/2) = 800 / 3
  34. Math

    h = initial balloon height , d = Patti/Ben distance h / d = tan(27º) ... h / tan(27º) = d (h + 35) / d = tan(36º) ... (h + 35) / tan(36º) = d (h + 35) tan(27º) = h tan(36º) ... 35 tan(27º) = h [tan(36º) - tan(27º)] solve for h , ...
  35. math/algebra

    the error is 5 mi 145 mi would be "rounded" to 150 mi
  36. science

    the angles are measured relative to the normal to the interface as the index increases, the ray is refracted more towards the normal , lessening the angle of refraction sorry, Steve
  37. science

    see Snell's Law increasing the refractive index would decrease the angle of refraction
  38. Physics

    here, here
  39. Physics

    uniform velocity (no acceleration) , means no force
  40. Scienve

    the potential energy at the high point is equal to the kinetic energy at the low point m g h = 1/2 m v^2 ... v = ?(2 g h) the mass is in kilograms , so the height is probably in meters v = ?(2 * 9.8 * 1.5) m/s
  41. Math

    13.65 * (1 + .035)
  42. maths

    n = 982 (1 + .09)^7
  43. Pre-Calc

    forgot the 1/3 in the volume equation
  44. Pre-Calc

    v = h * ? * (3/4 h)^2 = 9/16 * ? * h^3 v = 10 t h(t) = [160 t / (9 ?)]^(1/3)
  45. math

    the greatest common factor of 18 and 30 is ? that's how many bags
  46. Math

    it's a definition nCk = n! / [k! * (n-k)!] nC(n-k) = n! / {(n-k)! * [n - (n-k)]!} n - (n-k) = k
  47. Math

    y varies inversely with x ... x y = k find k to complete the equation
  48. Physical Science

    the braking force dissipates the kinetic energy of the vehicle if the velocity of the vehicle is doubled , the KE is quadrupled ... KE = 1/2 m v^2 ... so the brakes must dissipate four times the energy if the braking force is constant , it takes four times as long to stop
  49. Math

    there are eight possible sequences for three tosses HHH , HHT , HTH , THH , HTT , THT , TTH , TTT look at the descriptions of the sequences , and count the relevant outcomes
  50. Statistics

    symmetric around zero means the the two sides are the same shape zero is midway between -1 and 1 42% of the area is outside the -1 to 1 zone ... 21% on either side (symmetric) so the area to the right of 1 is 21%
  51. biology

    DNA carries the code (template) for making proteins (out of amino acids) RNA copies the code from DNA, and then assembles the protein
  52. Maths

    8C3 = 8C5 = 56
  53. physics

    the kinetic energy (which must be dissipated by the braking force) is proportional to the square of the velocity 3 times the velocity means 9 times the stopping distance
  54. Physics

    lower ... m g = k x ... weight = spring force drop ... m g y = 1/2 k y^2 ... potential energy at top = work to stretch spring 2 m g = k y ... substituting ... 2 k x = k y ... 2 x = y
  55. chemistry

    C is incorrect increasing pressure does not shift the equilibrium, so the gas volumes are equal on both sides of the equation ... B and A2B ... if A were a gas, the volumes would not be equal
  56. Physics

    h = -4.90 t^2 + 13.1 t t-max is on the axis of symmetry ... t = -b / 2a = -13.1 / (2 * -4.90) ... plug the time into the equation to find the max height plug half the max height into the equation to find the times (up and down)
  57. math

    1/6 is p(2) ... p(not 2) is 5/6
  58. Maths

    men ... 7C4 possibilities ... 35 women ... 8C3 possibilities ... 56 ... but 6 of the groups can't be used ... the incompatible pair with any of the other 6 women 35 * (56 - 6) = ?
  59. Geometry

    there is no direct calculation solution (it's an infinite series) use a calculator ... sin^-1 or arcsin or a table 12/16 = 3/4 = .75 ... remember, sine is positive in Quad I and II
  60. Vectors

    5 sin(15º) gives the vertical displacement (work against gravity) cosine gives the horizontal displacement
  61. math

    s + u = 12.5 16s + 10u = 160
  62. Science

    relative location of the light source (sun) water cloudiness ripples on water
  63. Math

    by inspection , about 1E11 ... only one even close
  64. Math

    internal base area ... 40 cm * 20 cm 8 L = 8000 cm^3 divide water volume by base area to find water height
  65. physics

    moles * Avogadro's constant = molecules
  66. Math (Algebra)

    cost = rate * minutes
  67. Math

    height difference is 4m 4m / RT = sin(30º)
  68. Math Statistics

    each term is the probability of that specific outcome n^x d^y means x were not defective and y were defective ... in this problem , x + y = 12 at least 4 defective means the sum of the terms where 4 or more were defective answers for these three were covered in your 1st posting
  69. Math Statistics

    check the original response
  70. Math

    at least 4 ... 1 - (first 4 terms) Exactly 1 ... second term 2 or more, but less than 5 ... (first 5 terms) - (first 2 terms)
  71. Math

    yes ... .9348
  72. Math

    when you expand the binomial , the 12, 66, etc. are the coefficients of the terms look up Pascal's Triangle for background
  73. Math

    this is a binomial probability ... defective or not defective probability (d) = .08 , probability (n) = .92 ... (n + d)^12 expand the binomial and substitute the probabilities in the desired terms ... n^12 + 12 n^11 d + 66 n^10 d^2 + ... + 66 n^2 d^10 + 12 n d^11 + d^12 less ...
  74. algebra 2

    2.29 m + 12.7 = 2.46 m
  75. Physics

    momentum is conserved in all these problems that is some BIG potato in #2
  76. Physics

    p * v = n * r * t n and t are changing ... if t increases , what happens to n?
  77. Physics

    temperature is a measure of the average kinetic energy ... 1/2 m v^2 what happens to KE if v is doubled?
  78. math

    this has been solved ... look in the list of similar questions
  79. Math

    1 = a + b -5 = 3a + b solve the system for a and b
  80. Algebra

    let m be the number of left-handed males , and f be the number of left-handed females m + f = 18 ... 8m + 8f = 144 8m + 6f = 130 subtracting (to eliminate m) ... 2f = 14 find number of right-handed females find fraction of right-handed students that are female
  81. physics

    convert the km/hr to m/s find the mass of the car find the KE of the car ... the work done stopping the car is equal to the KE work = braking force * stopping distance
  82. Math

    the angles are complementary ... sin alpha = cos beta = 1/3 sin^2 + cos^2 = 1 ... sin beta = ?[1 - (cos beta)^2]
  83. Calculus

    a --->? should probably be a --->0
  84. Math

    there are 5C3 ways of selecting a group of 3 from 5 there are 3! ways for a group of 3 to fill 3 positions 5C3 * 3! = ?
  85. algebra 2

    {(6-x)/[(x+7)(x-4)]} / {[(x+6)(x-6)]/[(x+9)(x-4)]} = [(6-x)(x+9)(x-4)] / [(x+7)(x-4)(x+6)(x-6)] = -(x+9) / [(x+7)(x+6)] x cannot equal -6 or -7 ... division by zero is a no-no
  86. Math

    (1 - .89) * 5.62 14) (1 - .76) * 57.41 15) (1 - .10) 48.69
  87. Math

    did not do the plot , just wanted to comment on the "inverse relation" stronger (and larger) linemen are usually slower than the smaller backs and receivers
  88. Math

    plot leg presses on the x-axis , and the corresponding 40 yd dash times on the y-axis then fit a line to the points (best fit)
  89. math

    did you read the "interest on the interest" part of the response?
  90. math

    compound means that in the 2nd year, interest is charged on the 1st year's interest he "owes" $200 plus the accumulated interest the answer choices are only the interest
  91. Algebra

    a) the max is on the axis of symmetry ... t = -b / 2a = -16 / (2 * -16) b) plug result from a) into the equation to find h c) he hits the water when h=0 ... 0 = -16t2 + 16t + 480 ... use quadratic formula to find t
  92. Math

    let 4x equal the 2nd angle x + 4x + 5x + 130 = 180
  93. Math

    natalia's sales total is below the mean for her class ... so if she moves to another class, the mean for her original class will increase natalia's sales total is above the mean for eric's class ... so if she moves to eric's class, the mean for the class will ...
  94. Algebra

    three cats can catch a rat per minute between them so the three can do the job
  95. kilauea

    search "hcl formation from lava reaction" apparently dissolved gasses in the lava play a major role
  96. Science

    junk ?
  97. Physics

    mass and radius are spurious information convert 33.5 rpm to rad/s ... multiply by ? and divide by 60 ... divide by 2 to find average angular velocity during acceleration convert 240º to radians ... multiply by ? and divide by 360 ... divide result by average angular ...
  98. Math

    height times the (average of the bases)
  99. math

    multiplying by 8 ... ?-30 = 0.32
  100. science

    the car has kinetic energy ... 1/2 m v^2 to stop the car; the work done by the brakes (f * d) must equal the car's kinetic energy (a) 1/2 * 1.00E3 * 35.0^2 = 8.00E3 * d (b) find the work done in 30.0 m and subtract it from the initial K.E. ... the remaining energy will ...
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