Wednesday
May 4, 2016

Posts by steve

Total # Posts: 40,143

maths
well, shucks -- what are cos(pi/3) and cos(pi/4)?
March 27, 2016

math @Reiny
The problem as stated above does not mention draining. However, your answer is one of the choices, so I guess his posting today was garbled.
March 27, 2016

math
None of those. the 4 gal of 25% antifreeze contains 3 gal water 1 gal antifreeze So, you need 2 more gal of antifreeze to make the result 50% algebraically, .25*4 + 1.00 x = .50(4+x)
March 27, 2016

math
600 * .30 + 300 * .60 = (300+600)x
March 27, 2016

math
20% of 36, of course
March 27, 2016

Math
Review your basic trig functions: the vertical height is y/120 = tan10° the distance walked is z/120 = sec10°
March 27, 2016

computer
I'm holding my flowchart up to the screen. Take a look. the algorithm is for n = 2 to 20 step 2   print n next n or, if you don't like for loops, i=1 n=2 NEXTI: print n n = n+2 i = i+1 if i <= 10 go to NEXTI stop
March 27, 2016

calculus2 - eh?
you want to try that again in complete sentences? The fragment when the casting temperature 1200 o C is bogus If this is a linear heat increase, no calculus is needed. If not, what model are you using?
March 27, 2016

Progression
we know that since b-a = c-b, x^c/x^b = x^b/x^a and the same for y and z. Try starting with that.
March 27, 2016

science
recall that the height h is h(t) = (500 sin30°)t - 5t^2 Now just find the vertex of that parabola.
March 27, 2016

math
the nature is easily found from the discriminant, B^2-4AC.
March 27, 2016

calculus
you know that |t-1| has a minimum at t=1, so 1-|t-1| will have a max there. Now just find the values at -9 and 6 and select the max and min
March 27, 2016

calculus
draw a diagram. Here is where implicit differentiation comes in handy. at the moment in question, the boat's distance x from the dock is 8 ft. The length of rope z is found by z^2 = x^2+8^2 so x^2 = z^2-64 x = √(z^2-64) Now start taking derivatives. The velocity and ...
March 27, 2016

calculas
just use the chain rule to get 18x + 128y y' = 0 Now just solve for y' and that's implicit, not explicit.
March 27, 2016

math
64*13 + 28
March 27, 2016

maths
so, did you draw the graph? Font problems in my browser caused your function to be garbled. Try typing it in, rather than copy/paste.
March 26, 2016

Math
well, it's the same as the probability of NOT choosing a green ball.
March 26, 2016

Pre Calculus
well, since profit is revenue less cost, P(x) = R(x)-C(x) you just need to solve for x in 0.002x^2 + 38x - 150000 >= 1650000
March 26, 2016

math
Your Algebra I is missing 3cos(x+4) = 1 cos(x+4) = 1/3 x+4 = arccos(1/3) x = arccos(1/3) - 4 = 1.231 also, 2π-1.231 = 5.052 sin^2(t) = 1/2 sint = ±1/√2 since sin π/4 = 1/√2 t = all odd multiples of π/4
March 26, 2016

contempory math
not enough to go on. All we have is A, 4G's, A, 5G's no telling how many G's we are expecting between the A's. 4,5 ... is not much info.
March 26, 2016

math
the diagonal has length √(8^2+8^2) = 8√2 So, the sides have length 8. The total area is thus 6*8^2
March 26, 2016

mathematics
Let x be Jane's age now y be John's age now They have said x+y = 25 (x-8) = 2(y-8) So, just solve for x and y.
March 26, 2016

TRIGONOMETRY
Or, more directly, tan = 1/cot = 1/√(cot^2) = 1/√(csc^2-1)
March 26, 2016

Math
product means multiply: x(x+2) = 80 Note that 8*10 = 80
March 26, 2016

calculas
if it's a max at t=0, it is a cosine curve. So, y(t) = (2.7/2) cos((2π/18) t) the velocity is y', so v(t) = -(1.35)(π/9) sin(π/9 t)
March 26, 2016

calculas
first, find the slope of the tangent line anywhere: y' = -3sin(3x) so, at x=π/4, y = -3sin(3π/4) = -3/√2 Now you have a point and a slope, so the line is y + 1/√2 = -3/√2 (x - π/4)
March 26, 2016

Math
66/36 = 18/x 66x = 18*36 x = 18*36/66
March 26, 2016

PRECALC
f(3+h) = 2^(3+h) = 8*2^h f(3) = 2^3 = 8 ... (g◦f)(5) / (f◦f)(3) = √(f(5)-7) / 2^f(3) = √(32-7) / 2^8 = 5/64
March 26, 2016

calc 2
g(x) = (x + 5/2)^2 - 25/4 p = -25/4 there are Euler's method calculators online.
March 26, 2016

Algebra 1
What grade represents a C? Let's say it's a 75. Then just consider the total points he needs to have a 75 average: 68 + p >= 2*75 If a C is some other number, then just make the adjustment and solve for p, the number of points he needs.
March 25, 2016

Probability
well, of the 52 cards, how may are a 3 or a K?
March 25, 2016

Math
42.5 <= 90-19x <= 52 -47.5 <= -19x <= -38 2.5 >= x >= 2
March 25, 2016

Probability
well, of the 52 cards, how many are a heart or a king?
March 25, 2016

mathematics-probability
well, the probability of getting a 6 on just the 1st roll is (1/6)^1 * (5/6)^3 Since you are allowed a 6 on any of the rolls, what do you think?
March 25, 2016

Math
2*8*6 + 2*3*6 + 2*3*8 = 180 in^2 How much she needs to buy depends on the width of the roll and how much overlap she uses during the wrapping.
March 25, 2016

Math
well, such a reflection takes (x,y) -> (-x,y) Now just plug in your numbers.
March 25, 2016

Math
you have a square of side 18 and 4 triangles with base 18 and height 12. So, since you know how to find the area of squares and triangles, just add 'em up.
March 25, 2016

math
14C5 = ?
March 25, 2016

Algebra
27 x^(-1 - 2/3) y^(-1 - 3/3) = 27 x^(-4/3) y^(-2) = 27 / x^(4/3)y^2
March 25, 2016

Algebra
if the initial speed is x, then since time=distance/speed, 400/s + 160/s + 240/(s-20) = 11
March 25, 2016

math
clearly, if there are x stacks of green & blue, and y of red & yellow, then 20x+14y = 300 10x+7y = 150 y = (150-10x)/7 y = 10(15-x)/7 Since there must be an integer number of blocks, and 7 does not divide 10, it must divide 15-x So, 15-x = 7 or 14 and y = 10 or 20 So, there ...
March 25, 2016

Maths
if the z is a typo, then you just have 2(sinx+cosx) = 3/2 sinx+cosx = 3/4 If the z is for real, then sinz + cosx = 3/4 cosx = 3/4 - sinz sinx = sqrt(1 - cos^2(x)) = sqrt(1 - (3/4 - sinz)^2) now just add sinx+cosx
March 25, 2016

geometry
Since the area is 1/2 r^2 θ, the ratio is 1/2 r^2 m∠AOB --------------- = (m∠AOB)/(m∠COD) 1/2 r^2 m∠COD That is, since for a given circle, the area is directly proportional to the angle, the ratio of the areas is the same as the ratio of the angles...
March 25, 2016

Calculus
If you walk a distance x, then the time t to reach the opposite corner is t(x) = x/s + √((a-x)^2 + 10^2) Now, just find dt/dx. The fastest time is when dt/dx=0, so plug in the fact that it is when x=0. Then you will get an equation is a and s.
March 25, 2016

Calculus
since x+y+z = 10, we want the max of F(x,y) = xy + (x+y)(10-x-y) Fx = -2x-y+10 Fy = -x-2y+10 Fx = Fy = 0 at (10/3,10/3) So, max of F(x,y) = 100/3 That is, when x,y,z are all equal, at 10/3.
March 25, 2016

math
If there are x kg of 30% alloy, then consider the total amount of copper in each part. It must add up to the total in the final alloy. .30x + .55(50-x) = .50*50
March 25, 2016

Math
that would, of course, be 1/7 * 2/3 = 2/21 cups Good luck on finding a measuring set to help you. Extra credit: How many tbsp is that?
March 25, 2016

Physics
Looks about right, if you use g=10 m/s^2
March 25, 2016

math
In terms of bricks, the wall's dimensions are 3300/22 = 150 350/7 = 50 40/10 = 4 150*50*4 * .9 = 27000 bricks That's just using raw volumes. However, if we add 10% to each brick's volume, we only need 24545 bricks. A more detailed analysis would add 3.23% to each ...
March 25, 2016

Physical
clearly it is either A or D. So, is there a numeric factor in there somewhere, or not?
March 25, 2016

Maths
That's theta not tita For ease of typing, I'll just use x. 2sinx + 2cosx = 1.5 sinx + cosx = 3/4 Now, since sin 45° = cos 45° = 1/√2, sinx + cosx = √2 sin(x+45°) Now we have sin(x+45°) = 3/(4√2) = 0.53033 x+45° = 32° x = -13&...
March 25, 2016

Science
watch the units: mass (g) = volume (cm^3) * density (g/cm^3) I doubt that the density if 7.8 g/cm^3. Make sure the volume units are correct.
March 25, 2016

Basic Arithematics
6650 * 0.94 * 1.10
March 25, 2016

Math
well, c = πd so, d = c/π
March 25, 2016

algebra 1 or pre algebra
well, just plug in the point. It is on the line, so it must satisfy the equation: -3 = 3*7 + b Solve for b. Then, recall that y=mx+b is the slope-intercept form of a line...
March 25, 2016

maths
what do you have against fractions? 3/8 + 1/4 = 3/8 + 2/8 = 5/8
March 25, 2016

physics
P = EI = 240*5 = 1200 = 1.2kW
March 24, 2016

Geometry
for the flagpole, draw a diagram. Draw a line parallel to the ground at the level of the top of the flagpole. The two angles mentioned are alternate interior angles, so they are congruent. the slope is the tangent of the angle. So, what angle x has tan(x) = 1/12 ? Take a look ...
March 24, 2016

Algebra
Just as with the baker, let x = acres of wheat y = acres of barley You want to maximize p=450x+350y subject to x+y >= 15 x+y <= 20 200x + 150y <= 2400
March 24, 2016

Algebra
If there are x packs of waffles and y packs of muffins, you want to maximize p = 1.50x+2.00y subject to 3/4 x + y <= 250 6x + 3y <= 1200
March 24, 2016

geometry
Or, using the formula area = 1/2 * apothem * perimeter, that will give you the perimeter. 1/5 of that will be the side length.
March 24, 2016

geometry
a regular pentagon has an apothem of 3.2 and an area of 37.2 cm. What is the length of one side of the pentagon?
March 24, 2016

english help please!!
google is your friend. I searched for marilyn cross pilot and got a bunch of hits on The Cold Equations, and discussions of the story and characters. I'd think you'd try google first before running here and expecting someone else to do your work for you. I know, I know...
March 24, 2016

algebra
I assume, but cannot be sure, that you meant f(x) = (x^4-4x^3)/(3-4x^2) + 1 since 3-4x^2+1 is kind of pointless. The denominator is zero when x = ±√3/2, so that is where the vertical asymptotes are. Before going any further, it'd be nice to know whether my f(x...
March 24, 2016

Calculus Applied Integrals
Just as a check, ∫[12.1,22.1] 1000 π (12.2^2)*9.8 x dx = 7.83595*10^8 which agrees with Damon's number, as expected.
March 24, 2016

@Engineers
Nice work, Damon. I like how the engineers always cut to the heart of the problem. Reminds me of the engineer's way to measure the area of an irregular shape. He traced it onto paper, cut it out, and weighed it. Then he weighed 1 cm^2 of paper, and voila! The area was easy.
March 24, 2016

Calculus Applied Integrals
What similar triangles? The tank has a circular cross-section of πr^2 Work = force (weight)*distance, so figure the weight of a thin slice of water (thickness dy). Then the work done to lift it over the top from depth y is its weight times y. Add up all those work pieces ...
March 24, 2016

Algebra
As always, draw a diagram. You will see that x/25000 = tan2°
March 24, 2016

mathematics-sequence
I had a question about 3-tails. Since no one else has offered to help, maybe you should explain how that applies here, rather than just reposting your same question with no additional data.
March 24, 2016

Trig Help
(b)The period is T=2π/(3π/4) = 8/3 s, so the frequency is 3/8 Hz Now, use T=2π√(L/g) to find L (d) since cos(π/2)=0, you want 3π/4 t = π/2 t = 3π/4 * 2/π = 3/2
March 24, 2016

Trig
using what I showed you earlier, what do you get?
March 24, 2016

Geometry
um, what in the above solution, did you not understand?
March 24, 2016

Geometry
a 4x5 card does not have the same aspect ratio as the 8.5x11 paper enlarging 4 to 8.5 is a scale of 2.125 enlarging 5 to 11 is a scale of 2.2 So, using the smaller scale, 4x5 enlarges to 8.5x10.625 or, 8 1/2 by 10 5/8 trying to enlarge it more will cause the width to exceed ...
March 24, 2016

Trig
sin(-θ) = -sinθ sec(-θ) = secθ cot(-θ) = -cotθ So, you have (-sinθ)(secθ)(-cotθ) = 1
March 24, 2016

Math
p * .75 * 1.07 = 67.41 Now just find p.
March 24, 2016

mathematics-sequence
not sure what you mean by "3-tails" The sequence is clearly just an arithmetic sequence.
March 24, 2016

math
If there are x kg of the 7.50 nuts, the rest (3-x) are 9.50 So, add up the cost of the amounts used. It must equal the final cost. 7.50x + 9.50(3-x) = 25.00
March 24, 2016

Calculus
If the ends are x and the other side is y, xy = 25600 So, the cost c(x) = 3*2x + 3/2 y = 6x + 38400/x so, dc/dx = 6 - 38400/x^2 dc/dx=0 when x=80 So, plug that in and find the minimum cost
March 24, 2016

physics
use T = 2π√(L/g) to get L. Now using that L, replace g with 0.29g to get the new T. .90 = 2π√(L/9.8) L = 0.201 .29*9.8 = 2.842 So, the new T = 2π√(.201/2.842) = 1.671 s ================================== Or, noting that T varies inversely as ...
March 24, 2016

Algebra
two cases: -2w+7 > 5 -2w > -2 w < 1 -(-2w+7) > 5 2w-7 > 5 2w > 12 w > 6 http://www.wolframalpha.com/input/?i=|-2w%2B7|%3E5
March 24, 2016

Math
yes it is.
March 24, 2016

MATH
My bad. You are correct.
March 24, 2016

MATH
why 1/5? 5 of the 10 digits are even.
March 24, 2016

Math
h(t) = 3 + 40t - 16t^2 Now just find the vertex of the parabola.
March 24, 2016

Algebra
8w^2+(8w)(5) = 1102 w = 9.5
March 24, 2016

math
5000*(1+.07*13) + 5000(1+.03/2)^(2*13) = $16,913.55
March 24, 2016

Algebra
the integers are 2k and 2k+2 (2k)*2(2k+2) = 160 k(k+1) = 20 20=4*5, so k=4 The numbers are 8 and 10
March 24, 2016

physics
look at the units: .5 cal/g°C * 10g * 10°C = 50 cal
March 24, 2016

algebra
first, expand the parentheses, so all the exponents are collected: a^2(ab^3)^2 = a^2 a^2 b^6 = a^4 b^6 b^2(a^2b^2)^2 = b^2 a^4 b^4 = a^4 b^6 Since all the variables have the same exponents, the terms can be added, giving a simple a^4b^6 + a^4b^6 = 2a^4b^6
March 24, 2016

Math
Just take the fraction of 100 for the group you want: 9/20 * 100 = ?
March 23, 2016

Math
do you mean 40-4k^3 if so, then for k=2, 49-4*2^3 = 40-4*8 = 40-32 = 8
March 23, 2016

MATHS GP
ar + ar^3 = 30 ar^5 - ar = 90 I get a=3 and r=2 The GP is 3, 6, 12, 24, 48, 96, 192, 384, ... T2+T4 = 6+24 = 30 T6-T2 = 96-6 = 90 T8 = 384
March 23, 2016

algebra
Don't knock BASIC. I knew a girl in college who was using it to program a gyroscopically stable table in orbit in 1972.
March 23, 2016

Math
(6.25-5.50)/5 = 0.15 min/km/mo now use that to form the equation.
March 23, 2016

Math- probabilities
well, what is the probability that NO ball is white? That is, 2 reds? Then take 1-P(red,red)
March 23, 2016

calculus
assuming the 80 ft is along the ground, h/80 = tanθ 1/80 dh/dt = sec^2θ dθ/dt when h=6, sec^2θ = 1+tan^2θ = 1+(6/80)^2 = 1.0056 1/80 dh/dt = 1.0056 * 4*π/180 dh/dt = 5.6 ft/s
March 23, 2016

mathematics-discriminant
hmmm. working with cubics? Gets messy. But, you should be able to find out that the discriminant is Δ = b^2c^2 - 4ac^3 - 4b^3d - 27a^2d^2 + 18abcd For your polynomial, that's just 99225 As wikipedia explains, For a cubic polynomial with real coefficients, the ...
March 23, 2016

math
add up all the times. If it's about 60 hours, then she's right.
March 23, 2016

Math
I need 27 2x4 50" long how many feet do I need
March 23, 2016

math
14*50 - 13*43
March 23, 2016

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