# 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

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

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

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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