Sunday
May 1, 2016

Posts by steve

Total # Posts: 40,046

word problems
naturally, when cost = revenue: 32x = 22x+1830 10x = 1830 x = 183
April 12, 2016

math
since time = distance/speed, d/12 + d/6 = 12
April 12, 2016

Algebra
you can get an idea of how these things work here: http://davidmlane.com/hyperstat/z_table.html try using your numbers, and you will see shaded areas.
April 12, 2016

Physics
nove height?
April 12, 2016

math
70 + 28n <= 1800
April 11, 2016

math investment problem
.05*4400 + .09x = 697.00
April 11, 2016

Math
clearly that would be 72/134
April 11, 2016

Business math - question help
400*1.1^14 + ... + 400*1.1^1 = 400(1.1^15-1)/(1.1-1) = 12709
April 11, 2016

science
recall that F = ma now plug in your numbers.
April 11, 2016

Math
mr and mrs smith, their 2 children and fog want to cross a river in a boat that would hold only 80 kg and both mr. amd Mrs Smith have a mass of 80 kg and both the children have a mass of 40 kg and the dog has a mass of 5 kg explain how they can cross the river in the fewest ...
April 11, 2016

Math
f' = 1 - 3/x^(2/3) = (x^(2/3)-3)/x^(2/3) f'=0 when x^(2/3) = 3 x^2 = 27 x = ±√27 the tangent is vertical at x=0. f increases where f' > 0: (-∞,√27)U(√27,∞) f decreases where f' < 0: (-√27,√27) The graph ...
April 11, 2016

Geometry
perimeter grows by a factor of 2, area by 4. So, find the existing values and then scale them up.
April 11, 2016

Math
well, the width is 7 and the height is 1.
April 11, 2016

Math
clearly the width is 7, since JK is a horizontal line. so the height is 1.
April 11, 2016

Geometry
I assume you can find the perimeter and area of the original pyramid. if the sides double, so does the perimeter. But the area, since it is the product of two sides, grows by a factor of 2^2, so it is 4 times as big.
April 11, 2016

Math
If CD=h and BC=x, then h/x = tan24° h/(x+7600) = tan16° or, h = 0.4452x h = 0.2867x + 2179.2649 0.4452x = 0.2867x + 2179.2649 BC = x = 13750 CD = h = 6121
April 11, 2016

Math
two distinct solutions means that the discriminant is positive. So, we need k^2 - 64 > 0 also, we need (k±√(k^2-64))/4 to be an integer. So, k±√(k^2-64) must be a multiple of 4. and k^2-64 must be an integer. so, what pythagorean triples do you ...
April 11, 2016

Math
the ball hits the ground when y=0. If you want a fraction, then let's get rid of the decimals: y = 1/10 (-49t^2 + 35t + 50) = 1/10 (7t+5)(10-7t) y=0 when t = 10/7
April 11, 2016

Pre algebra
6n-8 = 13 + 4(n+3) 6n-8 = 13+4n+12 2n = 33 n = 33/2
April 11, 2016

maths help!??
since time = distance/speed, 4/9 + x/2 = 1 That will tell you the rest of the distance. I suspect you have garbled your question, since they told you his speed for the first 4km was 9km/hr.
April 11, 2016

Math
translate up 3 means add 3 to all the y-values. left 3 and up 2 means subtract3 from x and add 2 to y. just think of the axes, and which directions are positive and negative. (4+2 , 3-5)
April 11, 2016

Algebra 2
tan^4 - sec^4 = (tan^2-sec^2)(tan^2+sec^2) = (tan^2-(1+tan^2))(tan^2+(1+tan^2)) = (-1)(1+2tan^2) = -2tan^2-1 Reiny, imagine the missing x's are present!
April 11, 2016

Math
the first digit must be 3,5,7 the other digits can be 1,3,5,7,9 since the 1st digit cannot be repeated, that means the last 3 digits must be formed using only 4 of the available choices, giving 4*3*2 choices. So, since the 1st digit can be chosen 3 ways, there are 3*4*3*2 ways...
April 11, 2016

Math
using the sum of tangents formula, tan(arctan x + arctan y) = tan(arctanx)+tan(arctany) ----------------------------- = tan(pi/4) 1 - tan(arctanx)-tan(arctany) (x+y)/(1-xy) = 1 x+y = 1-xy x+xy+y = 1
April 11, 2016

Factor out the Greatest Common Factor (GCF)
well, take a look 45d^3 = 9d^2 * 5d 18d^2 = 9d^2 * 2 so, what do you think?
April 11, 2016

maths
length = w+2
April 11, 2016

Calculus
check the related questions below. for extrema as described above, you need f' = 3ax^2+2cx = 0 at x=0 and -4, so x(3ax+2c) = 0 -12a+2c = 0 You also have two points, so -64a+16c+d = 9 0a+0c+d = 6 a = 3/32 c = 9/16 d = 6 so, that means that f(x) = 3/32 x^3 + 9/16 x^2 + 6 the...
April 11, 2016

Math
Remember your Algebra I. The max height is represented by the vertex of the parabola. As with all quadratics, the vertex is at t = -b/2a. So, for #1: t = -122/-32 = 3.8125 seconds use the same logic on #2.
April 11, 2016

Vectors, Math
Since |B| = 4, B = <4/√2,-4/√2> = <2√2,-2√2> AB = B-A = (2√2-3,-2√2-2)
April 11, 2016

math
b/a = tan 60° = √3 The ratio of the volumes is thus πb^2a/πa^2b = b/a = √3
April 11, 2016

calculus 2
What, you don't have any work to show? You can verify your results using the handy calculator at http://keisan.casio.com/exec/system/1392171850
April 11, 2016

fds
all of them
April 11, 2016

math
you might show your work, so we could check your method. each dogs eats 3.5/7 = 0.5 kg/day 16 dogs eat 8 kg/day That's 720 kg for 90 days Or, 1584 lbs. That's 63.36 bags I guess it depends on how many days you use for 3 months. 91 days gives 64.06 bags
April 10, 2016

Math geometry
w/146 = cot 50°
April 10, 2016

Geometry
you are correct if the "thickness" means the height of the material on the ground.
April 10, 2016

Calculus derivatives
well does that not mean that dy/dx = -1? Using implicit differentiation, 2x + y + xy' + 2yy' = 0 y' = -(2x+y)/(x+2y) so, you want (2x+y)/(x+2y) = 1 2x+y = x+2y y = x plug that into the original equation and you get x^2 + x^2 + x^2 = 1 x^2 = 1/3 so, at (1/√3,1...
April 10, 2016

Math
If there are x wheat and y oats, x <= 200 y <= 300 x+y <= 250
April 10, 2016

Math :)
I'd say high volume, since that minimizes the surface area, making the cube last longer. High surface area (lower volume) means faster cooling, but the cube does not last as long.
April 10, 2016

Calculus
nope 4x/(x-5) -> 20/0 this is just algebra. Recall your rational functions work? Vertical asymptote at x=5.
April 10, 2016

Math
If Owen has x and Charley has y, then we are told that x-50 = y+50 (x+100) = 4(y-100) Now just find x.
April 10, 2016

Calculus
This is just ∫∫∫ dz dy dx using the appropriate limits Unfortunately, the plane 2x+z=3 is a vertical plane, and does not bound a region of the paraboloid.
April 10, 2016

math
8914*1.0136^t = 15000 t = 38.53 Better check your math.
April 10, 2016

Math
these are headings, not bearings. I do not get a right triangle. I get an angle of 27+90+27= 144 at the turning point. To get the final location, convert each side to its x- and y-components. Add them up, and you can then get the angle θ using tanθ = y/x and then the...
April 10, 2016

Math: Parametric Equations
since sin^2(t)+cos^2(t) = 1, (2+4cos(s))^2 + (3+4sin(s))^2 = 1 See where that gets you.
April 10, 2016

maths
set up a diagram. You can see that if the angle to the top of the building is a, then x/9 = cot(a) x/16 = cot(a+θ) θ = arctan(x/9) - arctan(x/16) dθ/dx = 0 when x=12 as shown here: https://www.wolframalpha.com/input/?i=arctan%28x%2F9%29+-+arctan%28x%2F16%29
April 10, 2016

maths
tan(A/2)
April 10, 2016

math
Assuming the usual carelessness with parentheses, I get 4^(x+3) = 32(2^(x+y)) 2^(2(x+3)) = 2^5*2^(x+y) 2x+6 = 5+x+y x = y-1 9^(y-1) + 3^y = 10 3^(2y-2) + 3^y = 10 3^(2y)/9 + 3^y = 10 3^(2y) + 9*3^y - 90 = 0 (3^y + 15)(3^y - 6) = 0 3^y = 6 y = log6/log3 x = y-1 That answer is ...
April 10, 2016

maths
logy/log2 = log_2(y) logy/log4 = log_4(y) since 2^2 = 4, log_2(y) = 2log_4(y) = log_4(y^2) so, now we have log_4(y^2*y) = 6 log_4(y^3) = 6 y^3 = 4^6 y = 4^2 = 16
April 10, 2016

math
2lg5 = lg(5^2) lg[(x+14)/(x-2)] = lg25 (x+14)/(x-2) = 25 x+14 = 25x-50 24x = 64 x = 8/3
April 10, 2016

geometry (check answers)
a no b many c many d one e no f no
April 10, 2016

Calc
a little check will show that h = A/w - w/4 So, the perimeter is (assuming the triangle is isosceles) p = w+2h+w√2 = w(1+√2) + 2(A/w - w/4) = (1/2 + √2)w + 2A/w dp/dw = (1/2 + √2) - 2A/w^2 dp/dw = 0 when w = 2√(A/(2+√2)) h = (1+√2)/2...
April 9, 2016

LOGARITHM
Assuming you meant the log of (2x-1)^2, then that means (2x-1)^2 = e^7 2x-1 = e^3.5 = 33.115 2x = 34.115 x = 17.0577 Looks ok to me. of course, there is the other root using 2x-1 = -33.115
April 9, 2016

Math: Parametric Equations
cos(4t) has period pi/2 sin(6t) has period pi/3 so, you get the entire curve using the interval [0,pi] as indicated by the note next to the graph at the suggested URL.
April 9, 2016

Math
of course he is right. The actual room is 18 times as big as the drawing. So, any length on the drawing, times 18, is the length in the room. Any length in the room, divided by 18, is the length in the drawing. That's the whole purpose of scale drawings - to represent the ...
April 9, 2016

History
indeed
April 9, 2016

History
What powers did Parliament have in the Bill of Rights?
April 9, 2016

Math: Trigonometry
we want sin(x+n) = cos(x) sin(x)cos(n) + cos(x)sin(n) = cos(x) we need cos(n)=0 and sin(n)=1 This is true only for n = 2k*pi + pi/2 for k=0,1,2,3... that is pi/2, 5pi/2, 9pi/2, ... 100 * 2/pi = 63.6, so the last entry in the list is 61pi/2 = 95.8
April 8, 2016

History
thanks
April 8, 2016

History
yes i would like help with the assignment, like good sites onto where i could find information of this or something
April 8, 2016

History
1. What powers did Parliament have in the Bill of Rights? 2. Why was King James removed from the throne? 3. Do you think the people of England were more in favor of King William and Queen Mary in being the King and Queen than King James II? Why or nor why not? Support your ...
April 8, 2016

Algerba
sure thing. When you encounter complicated math problems, just take a deep breath and realize that since you only know a few simple rules for working with the stuff, the big mess can always be broken down into simple pieces that you can do easily, using the rules you know.
April 8, 2016

Algerba
sure. Note that 4-4=0, so that term goes away. Also, 4/2 = 2. Then you have 3r- 4/2 +4r-12+13s+5r+5(9-r)-6r+2(-4)-5(2s)+2(9+3r)+2-3s = 57 remove the parentheses: 3r-2+4r-12+13s+5r+45-5r-6r-8-10s+18+6r+2-3s = 57 Now collect all the r and s stuff, and collect all the constants: ...
April 8, 2016

Algerba
ah. never mind. After you clear away all the noise, you are left with 7r+43 = 57 7r = 14 r = 2 the value of s does not matter; it can be anything.
April 8, 2016

Algerba
still, you want r or s?
April 8, 2016

Algerba
you have two variables, and unmatched parentheses. You want to solve for r or s?
April 8, 2016

Calculus
works for me. I did the integral directly, using ∫[0,1] 2π(1-y) arccos(y) dy and got the same answer. I like your technique of avoiding the arccos, though.
April 8, 2016

Math
better look up the inflation rates between then and now.
April 8, 2016

Math 10- Relations & Functions
y = 4x-8 C(n) = 14n+5 8x+12 = 132 F(6) = 8*6 + 12
April 8, 2016

Math Help!!!
looks good to me.
April 8, 2016

geometry
I'd start with this: The circle's equation is (x - a/2)^2 + (y - b/2)^2 = (a^2+b^2)/4 If a chord intersects the x-axis at x=c, then the slope of the chord is (b)/(a-c) so, the equation of the chord is y = b/(a-c) (x-c) and the length of the chord is 2sqrt((a-c)^2 + b^2...
April 8, 2016

Algebra
√363 - 3√27 = √(121*3) - 3√(9*3) = 11√3 - 3*3√3 = 2√3
April 8, 2016

Algebra 1
n = n^1 so, adding exponents, n^-4•n = n^-4 • n^1 = n^(-4+1) = n^-3 or, since n^-4 = 1/n^4, 1/n^4 • n = n/n^4 = 1/n^3
April 8, 2016

mathematics
all sides are 10, so its base is 10. 10h = 84 h = 84/10 = 42/5
April 8, 2016

Math
well, what is 100% of 25? Naturally, that's 25, since 100% is all of something. 500% is 5 times 100%, so that is just 5*25 = 125 a little thought can help a lot while you're waiting, rather than whining about it.
April 7, 2016

Mathematics
yes. the angle is 1/5 of 360°, or 72° and that's rotational symmetry, not system.
April 7, 2016

math
4.1x10^5 = 4.1 x 100,000 = 410,000
April 7, 2016

Math
10*9*8 = 720
April 7, 2016

Algebra
-7 < y <= 3
April 7, 2016

Math
1/5 + 1/4 = 9/20 so, the rest is 11/20 11/20 x = 11 so, 1/20 x = 1 x = 20 1/5 of 20 is 4 to her brother
April 7, 2016

calc 2
for our function, y' = 6k(kx)^5 so, we want other curves whose slope is y' = -1/(6k^6) x^-5 y = 1/(24k^6 x^4) or, to make things look more similar, y = 1/(24k^2) (kx)^-4
April 7, 2016

Newtons Second Law
Net force is 7500-2200-5000 = 300N F = ma, so a = 300N/1200kg = 0.25 m/s^2 the actual speed of the car does not matter.
April 7, 2016

Algebra
The fill rate is clearly 825 ft^3/hr At 10 hours, that will be 8250 ft^3. no idea of the percent filled. How big is the silo?
April 7, 2016

pre ap math
cool!
April 7, 2016

Math
factor out the 9: 9(y^2-9) difference of squares: 9(y-3)(y+3)
April 7, 2016

Algebra
If there were x oz of almonds, then the rest (300-x) was tea. 0.95x + 2.15(300-x) = 1.85(300)
April 7, 2016

Math
3 yds = 108 in. So, length+width = 54 in. Starting with w=6, we thus have dimensions of 6,48 7,47 ... 12,42
April 7, 2016

Algebra
looks good to me.
April 7, 2016

Algebra
1/5 + 1/12 = 1/x
April 7, 2016

chemistry
66s is 6 half-lives, so 49.0 * (1/2)^6 = 0.765 μg
April 7, 2016

Chemistry
80(1/2)^t = 10 (1/2)^t = 1/8 t = 3 so, 45 days is 3 half-lives
April 7, 2016

Math
42
April 7, 2016

Algebra
since time = distance/speed, 132/(x+11) = 132/x - 2 x = 22 6 hrs at 22 mph 4 hrs at 33 mph
April 7, 2016

Algebra
If it takes A x days, it takes B 2x days. 1/x + 1/(2x) = 1/5 3/(2x) = 1/5 x = 15/2 So, it takes B 15/2 days, and A 15/4 days
April 7, 2016

Algebra II
so, 8=4p p=2 that is the distance from the vertex to the focus. All you need to do is (a) read what we gave you (b) think about it a bit
April 7, 2016

Algebra II
for the parabola y^2 = 4px the vertex is at a distance p from the focus.
April 7, 2016

Math
which are the right angles?
April 7, 2016

chemistry
142km * 1gal/27mi * .6214mi/km * 3,78L/gal = 12.35L
April 7, 2016

Algebra
If x at 2 pts, then 24-x at 3 pts. So, adding up all the points, 2x + 3(24-x) = 53 x = 19 for 2-pts so, 24-x = 5 for 3-pts
April 7, 2016

math
In QI, x>0 and y>0 so, where are x<0 and y<0 ?
April 7, 2016

Chemistry
What is the mole fraction of NaBr in an aqueous solution that contains 20.1% NaBr (weight/weight%)?
April 7, 2016

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