Posts by Scott
Total # Posts: 4,107

statistics
46 is 3 standard deviations below the mean 
math
like the 1st question , only different numbers use the same technique term value = 1st term + [difference * (term number  1)] 
math
the difference between consecutive terms is 4 106 = 2 + [4 * (n1)] ... solve for n , the term number 
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? 
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? 
Physics
oops ... decimal error ... should be ... 6.0 ± 1.7% sorry 
Physics
when quantities are multiplied , percent errors are added (6.0 ± .17%) * (4.0 ± 5%) = ? 
Math
"Females outnumber males by 200, so there are 800 females and 400 males" ... does that look correct? maybe 700 and 500? 
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 
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 ... 
Chemistry
find the mole weights x + 2y = 100 3x + 2y = 180 solve the system for x and y 
Math probability
the zscore is the number of standard deviations (?'s) that a value lies from the mean the zscore table gives the probability of a score's position in a normal distribution eg. the table gives the mean (zscore, zero) a probability of .5 ... half of the population ... 
mathdistinguishability
library  out ... 5  1 , 4  2 , 3  3 , 2  4 , 1  5 
Math
solve the system of equations for x, y, and z those are the coordinates of the point of intersection 
science
the Earth rotates on its axis and revolves around the Sun 
math
what you say you know is incorrect all 52 cards in a deck are different 
Maths
you have two sides of a right triangle ... the distance is the hypotenuse a^2 + b^2 = c^2 
Math
28% off means that the sale price is 72% of the regular price ... 100%  28% = 72% .72 * p = $666.00 
Physics
the horizontal velocity is constant regardless of height ... the vertical velocity changes due to gravity horizontal velocity = 15 m/s * cos(45º) 
Chemistry
CH3CO2H ? CH3CO2? + H+ [CH3CO2?] [H+] / [CH3CO2H] = 1.8E5 x^2 / (.25  x) = 1.8E5 ... x^2 + 1.8E5 x  4.5E6 = 0 ... x = 2.11E3 log(2.11E3) = 2.67 ... good choice 
maths
google 7 digit primes ... it's a long list 
Math
probability of miss ... 1  3/4 = 1/4 probability of two misses in a row ... 1/4 * 1/4 = ? 
Math
... like 16 and 7 ... 
Math
radical 16 ... ?16 ... equals ±4 ... a rational number the product of two rational numbers is rational 
Chemistry
right 
Chemistry
[F]^2 / ([C] [A]^2) 
math
you're going to subtract 4 from x ... and the result is greater than zero keep thinking 
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 
algebra
5 * 54 = x * 45 
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 
Math
40000 * [1 + (.025 * 12)] 
Math
adding 7 , then subtracting 5 look at two sets of every other term ... 3  5  7  9  ...  10  12  14  16 
Math
xmax is on the axis of symmetry of the parabola b / 2a = 800 / (2 * 3/2) = 800 / 3 
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 , ... 
math/algebra
the error is 5 mi 145 mi would be "rounded" to 150 mi 
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 
science
see Snell's Law increasing the refractive index would decrease the angle of refraction 
Physics
here, here 
Physics
uniform velocity (no acceleration) , means no force 
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 
Math
13.65 * (1 + .035) 
maths
n = 982 (1 + .09)^7 
PreCalc
forgot the 1/3 in the volume equation 
PreCalc
v = h * ? * (3/4 h)^2 = 9/16 * ? * h^3 v = 10 t h(t) = [160 t / (9 ?)]^(1/3) 
math
the greatest common factor of 18 and 30 is ? that's how many bags 
Math
it's a definition nCk = n! / [k! * (nk)!] nC(nk) = n! / {(nk)! * [n  (nk)]!} n  (nk) = k 
Math
y varies inversely with x ... x y = k find k to complete the equation 
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 
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 
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% 
biology
DNA carries the code (template) for making proteins (out of amino acids) RNA copies the code from DNA, and then assembles the protein 
Maths
8C3 = 8C5 = 56 
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 
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 
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 
Physics
h = 4.90 t^2 + 13.1 t tmax 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) 
math
1/6 is p(2) ... p(not 2) is 5/6 
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) = ? 
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 
Vectors
5 sin(15º) gives the vertical displacement (work against gravity) cosine gives the horizontal displacement 
math
s + u = 12.5 16s + 10u = 160 
Science
relative location of the light source (sun) water cloudiness ripples on water 
Math
by inspection , about 1E11 ... only one even close 
Math
internal base area ... 40 cm * 20 cm 8 L = 8000 cm^3 divide water volume by base area to find water height 
physics
moles * Avogadro's constant = molecules 
Math (Algebra)
cost = rate * minutes 
Math
height difference is 4m 4m / RT = sin(30º) 
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 
Math Statistics
check the original response 
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) 
Math
yes ... .9348 
Math
when you expand the binomial , the 12, 66, etc. are the coefficients of the terms look up Pascal's Triangle for background 
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 ... 
algebra 2
2.29 m + 12.7 = 2.46 m 
Physics
momentum is conserved in all these problems that is some BIG potato in #2 
Physics
p * v = n * r * t n and t are changing ... if t increases , what happens to n? 
Physics
temperature is a measure of the average kinetic energy ... 1/2 m v^2 what happens to KE if v is doubled? 
math
this has been solved ... look in the list of similar questions 
Math
1 = a + b 5 = 3a + b solve the system for a and b 
Algebra
let m be the number of lefthanded males , and f be the number of lefthanded females m + f = 18 ... 8m + 8f = 144 8m + 6f = 130 subtracting (to eliminate m) ... 2f = 14 find number of righthanded females find fraction of righthanded students that are female 
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 
Math
the angles are complementary ... sin alpha = cos beta = 1/3 sin^2 + cos^2 = 1 ... sin beta = ?[1  (cos beta)^2] 
Calculus
a >? should probably be a >0 
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! = ? 
algebra 2
{(6x)/[(x+7)(x4)]} / {[(x+6)(x6)]/[(x+9)(x4)]} = [(6x)(x+9)(x4)] / [(x+7)(x4)(x+6)(x6)] = (x+9) / [(x+7)(x+6)] x cannot equal 6 or 7 ... division by zero is a nono 
Math
(1  .89) * 5.62 14) (1  .76) * 57.41 15) (1  .10) 48.69 
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 
Math
plot leg presses on the xaxis , and the corresponding 40 yd dash times on the yaxis then fit a line to the points (best fit) 
math
did you read the "interest on the interest" part of the response? 
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 
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 
Math
let 4x equal the 2nd angle x + 4x + 5x + 130 = 180 
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 ... 
Algebra
three cats can catch a rat per minute between them so the three can do the job 
kilauea
search "hcl formation from lava reaction" apparently dissolved gasses in the lava play a major role 
Science
junk ? 
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 ... 
Math
height times the (average of the bases) 
math
multiplying by 8 ... ?30 = 0.32 
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 ...