Monday
March 30, 2015

Posts by Steve


Total # Posts: 30,192

programming concepts
to find the average, just add up all the numbers and divide by how many there are. That means you have to count them as you read them.
March 27, 2015

Math
cool. Look. We don't mind helping find answers, but at least can we expect not to have to provide the question as well?
March 26, 2015

Math Venn Diagram
Did you make a Venn diagram yet? Put any numbers in it? Start with the 4 in the middle. Then work your way out from there.
March 26, 2015

Math
4*6*(5-x) = 2*4*6* 5-x = 2 x = 3
March 26, 2015

Math
9*pi*1.2 units/min
March 26, 2015

geometry
yep. so stipulated.
March 26, 2015

Math
9*3.77 units/min
March 26, 2015

pre algebra
well, how much after one payment?
March 26, 2015

Physics
If A is moving in the positive direction, then we must have zero total momentum before and after the collision: 10(15) + m(-5) = 0
March 26, 2015

math
well, if the original radius is r, we have π(r+1)^1 = 100π Or, just note that it's obvious that a radius of 10 gives an area of 100π, so the original radius was 9.
March 26, 2015

Math 115
You have any thoughts on any of these?
March 26, 2015

Math 115
If the cheap sides are x, and the expensive side is y, then xy = 320 c(x) = 6*2x + 6y + 14y = 12x+20y = 12x + 20(320/x) c'(x) = 12 - 6400/x^2 minimum cost is at x = 80/√12 ≈ 23 So, the area is roughly 23 by 14 (That's 322 ft^2)
March 26, 2015

Math 115
P = R-C that will be a parabola. Find its vertex.
March 26, 2015

Math
Look. If I said I had to pick 10 apples, but I only had 7 so far, how would you decide the number I still needed? Don't let the fractions scare you. They're just numbers.
March 26, 2015

Math
subtract what he has from the total.
March 26, 2015

math
f(x) = cx/(2x+3) f(f) = cf/(2f+3) = c[cx/(2x+3)]/(2[cx/(2x+3)]+3) = c^2x/(2(c+3)x+9) So, if c^2x/(2(c+3)x+9) = x, c^2x = 2(c+3)x^2 + 9x 2(c+3)x^2 + (9-c^2)x = 0 x(2c+6+9-c^2) = 0 x(15+2c-c^2) = 0 x(5c-1)(3c+1) = 0 So, c = 1/5 or c = -1/3
March 26, 2015

Algebra
f(x) = 2(x-1)^2 - 7 So, if we restrict the domain to x>1 or x<1 we can find an inverse
March 26, 2015

math
h = 1/√x h^2 = 1/x x = 1/h^2 so, h^-1(x) = 1/x^2 h^-1(4) = 1/16
March 26, 2015

algebra
since g(x) is a parabola, there are two values of x for every value of g. So, there is no inverse. However, if you pick a single branch of the parabola (that is, you restrict the domain), there is an inverse.
March 26, 2015

Math
Convert 22 miles to yards. Use a proportion to solve. Show your work. Where do I start with this problem?
March 26, 2015

calc
f is a polynomial, so it is continuous and differentiable f(4) = f(0) = 8, so that's ok So, you want c where f'(c) = 0 That means you need 3c^2 - 2c - 12 = 0 c = 2.361 The other value is not in [0,4]
March 26, 2015

Math
starting from M, you go 74 SE and 42 W That is (52.33,-52.33) + (-42,0) = (10.33,-52.33) tanθ = -52.33/10.33 = -78.8° So, the bearing is 168.8° or E 78.8° S or S 11.2° E
March 26, 2015

5th grade math
80 <= 1.22n <= 85 divide through by 1.22 and you get 65.57 <= n <= 69.67 If you want only integer values for n, then that would be any of 66,67,68,69
March 26, 2015

geometry
not sure how I'd do it without trig. Any clever geometric relationships that make it easy?
March 26, 2015

geometry
in triangle PQS. sinP/9 = sinQ/8 = sinS/5 So, you can find angle P Now, using the law of cosines in triangle PRT RT^2 = 10^2 + 16^2 - 2*10*16*cos(P)
March 26, 2015

calculus
p(8) = 1536 p(4) = 192 so, avg v is (1536-192)/(8-4) = 336 p'(t) = 9t^2 so, you want 9c^2 = 336
March 26, 2015

7th grade math (probability)
They all look good to me.
March 26, 2015

math
Huh? You said above what the vertex is. as always, it is at t = -b/2a It is not at t=3, but very close. Probably good enough.
March 26, 2015

math
clearly there is an x-intercept somewhere just beyond 6. See how the height is descending. Since the given h values do not show an obvious symmetry, it is not immediately clear where the vertex is. However, since h(0) = 0, if h(t) = at^2 + bt + c c = 0, so h(t) = at^2 + bt ...
March 26, 2015

math
try writing fractions like this: 2/3 + x/4 = 4/7
March 26, 2015

Algebra
two real roots
March 26, 2015

Math
well, just work from the inside out 2/3 - 1/3 = 1/3 so, what you have without the brackets is 1/3 * 5/8 = 5/24
March 26, 2015

Math
1 yd = 3 ft (1 yd)^3 = (3 ft)^3 = 27 ft^3
March 26, 2015

Algebra 1
(66-6)/6 = 10 (77-7)/7 = 10
March 26, 2015

^math^
√(19-4√21) since 21 = 19+2, I'd check (2-√21)^2 = 4-4√21+21 nope (1-2√21)^2 = 1-4√21+42 nope (2√3-√7)^2 = 12-4√21+7 aha!
March 26, 2015

MATH
.08x - .05(36000-x) = 2750
March 26, 2015

algebra
simple interest, yes compound interest, no
March 26, 2015

math
didn't my solution in the related question below do the job?
March 26, 2015

math
-3 It helps a bunch if you use a caret (^) to indicate exponents. As in (10^6)^-3 = 10^-18
March 26, 2015

science
1st step: figure how many moles of each you have. Then figure the fraction.
March 26, 2015

math
well, you know the formula for the area of a triangle, so plug in your numbers 30h/2 = 600
March 26, 2015

algebra
for substitution, I would, um, substitute. The 1st equation tells you that y = -2x So, substitute that into the 2nd equation to get x-3(-2x) = -7 x+6x = -7 7x = -7 x = -1 Now you can find y. As for elimination, 3x + 4y = 1 5x – 3y = 21 to eliminate y, multiply the 1st by ...
March 26, 2015

Geometry
just solve 2(3x+10 + x+12) = 76 then you can figure the length and width, and thus the area.
March 26, 2015

math
see related question below
March 26, 2015

Math
just as you would any quadratic: 1.862t^2 - 50t - 2 = 200 1.862t^2 - 50t - 202 = 0 t = (50±√(50^2 - 4(1.862)(-202)))/(2*1.862) = (50±√4004.496)/3.722 = (50±63.281)/3.722 = -3.566 or 30.419
March 26, 2015

math
the dimensions are x,y,3
March 26, 2015

Math
false 6x1 You can only multiply two matrices if the columns of the 1st are the same as the rows of the second. That is, the dimensions must be of the form axb and bxc a and c may be anything, but the b's must match. The result is axc.
March 26, 2015

Math
just solve 2^(-t/1590) = 1/5 since 2^-2 = 1/4, you should expect an answer something more than two half-lives.
March 26, 2015

Math question
33+55-14 = 74 students liked something That means 26 liked nothing So, the number not liking orange is 26+(76-33) = 69 How did you arrive at 67? As usual, check my math
March 26, 2015

math
(1060-560)/1060 * 100 = 47%
March 26, 2015

Calculus 2 (Differential Equation)
If we pick a different c, the solution looks a little more symmetric, and more like the original equation: y = sin(arcsin(x)+arcsin(c)) y = sin(arcsin(x))cos(arcsin(c)) + cos(arcsin(x))sin(arcsin(c)) = x√(1-c^2) + c√(1-x^2) Just a thought. A bit ugly because c ...
March 26, 2015

Math
2m = 200 cm so, subtract the 15, and what do you have left?
March 26, 2015

Physics
since 1A = 1C/s, you have a current of 1C/.09s = 11.11 amps now just recall your formulas for power and energy
March 25, 2015

Math if my answer is correct
I get -0.04 and 26.89 what did you do to get your answers?
March 25, 2015

Math
That's what I get
March 25, 2015

algebra
It can indeed be either, depending on whether you are given a set of six letters, or allowed to choose your own six from the whole alphabet.
March 25, 2015

physics
how long does it take to fall? 4.9t^2 = 310 so, its downward speed is v = 9.8t
March 25, 2015

algebra
y >= 4x-5 For inequalities, the solution is a whole set of numbers, not just one. Plot the line y = 4x-5 Your inequality as as its solution everywhere in the whole x-y plane which is above that line, since that is where y is greater than the values lying on the line. The ...
March 25, 2015

math
since 72° is 1/5 of 360°, 3 slices is 1/5 of the pie. That help? The real question is, how the heck do you cut a pie into an odd number of equal slices?
March 25, 2015

physics
F = ma what's the trouble? Forget your Pythagorean Theorem?
March 25, 2015

math
since the concentrate is 100% juice, and the water is 0% juice, we have 100x + 0(12-x) = 15(12) x = 1.8
March 25, 2015

math
.36x + .50y = .37(100) Your language should read One equation in a system for solving this problem is x+y=100. What is the other equation? Since you gave no choices...
March 25, 2015

algebra
man! what a lot of words! Why not just list the points on the graph? (4,-4),(3,-3),(5,-3) Right there we see the vertex is at (4,-4), so y = a(x-4)^2 - 4 Now we have points (1,5),(7,5) 5 = a(-3)^2 - 4 = 9a-4 a = 1 so, y = (x-4)^2 - 4
March 25, 2015

Math
x/2 - 1 = (x-1)/3 x = 4 half of 4 is 2 yellows to start with less 1, leaves 1 yellow of 3 birds left
March 25, 2015

math urgent
recall the projection of b on a: p_a(b) = a.b * a/(a.a) v1 = u1 = (1,2,0) v2 = u2 - p_v1(u2) = (1,0,0) - (1/5,2/5,0) = (4/5,-2/5,0) v3 = u3 - p(u3,v1) - p(u3,v2) = (1,0,1) - (1/5,2/5,0) - (4/5,-2/5,0) = (0,0,1) check: v1.v2 = 4/5 - 4/5 = 0 v1.v3 = 0 v2.v3 = 0 so, v1,v2,v3 are ...
March 25, 2015

Calc
If y is the number of rebates, then the revenue is r(y) = (420-16y)(1300+160y) assuming only enough sets are made to sell out, then x = 1300+160y so, the profit is revenue less cost p(y) = r(y) - c(1300+160y) = (420-16y)(1300+160y) - (91000+140(1300+160y)) = -2560y^2 + 24000y...
March 25, 2015

Math/Science
there are 1000 micros per milli so, 10mm = 10,000 µm Since 1m = 1000mm, 10mm = 0.01m You did your conversion just backwards.
March 25, 2015

Math
??? if 4.8 ml must be added, I'd say the volume is 4.8 ml What am I missing? or, How has the question been garbled? Maybe you should clarify just what the named volumes comprise.
March 25, 2015

math
Unless we know how many students belong to more than one of the groups, there is no way to know how many total students were sampled. So, any or none of the choices could be correct.
March 25, 2015

Math
A (or any of the answers!) is correct only if there are exactly 100 stamps in all. All we are told is that there are 5% more from Norway than from France. If there are 1000 stamps, then there are 50 more, not 5.
March 25, 2015

math - question stuck!
if x is the combined mass of truck and wheat, and b is the # bushels, then b-300 = (500-300)/(21.6-16.2) (x-16.2) b = 37.037x - 300 so, find x when b=600 Now, if the truck weighs t and each bushel of wheat weighs w, we have t + 300w = 16.2 t + 500w = 21.6 so, w = 0.027, and t...
March 25, 2015

Comprehensive Science
You are correct.
March 25, 2015

Alg. 2
just plug in the numbers, assuming p(t) = ae^kt p(0) = 35000, so a = 35000 p(15) = 35000 e^15k = 21000, so k = -0.034 p(t) = 35000 e^-.034t e^-.034 = 0.9665, so the population is decreasing by 3.35% per year
March 25, 2015

math proportions
1 1/6 is 1/3 of 3 1/2 so, to do the job in 1/3 the time, we need 3 times the editors, or 15 Or, since the amount of work is constant, (3 1/2)(5) = (1 1/6)(x) x = 15
March 25, 2015

Math
in feet, the dirt is (9)(16)(1/3) = 48 ft^3 so, just divide that by 27 and multiply by the cost per cubic yard of dirt.
March 25, 2015

math
You just gave an example. Go ask 20 visitors their age. That's probably not a good example, since it's fairly hard to pick truly random people. But, you might count the number of people entering or leaving in a certain time period, and tracking that value over the ...
March 25, 2015

Algebra (Math)
these are just vertical or horizontal lines. clearly, the first set of equations intersect at (2,-3) The second intersect where y=2 so, plugging that into the second equation, x+2*2=10 x = 6 and they intersect at (6,2) Having said that, and solved the systems, go ahead and ...
March 25, 2015

Math
note that each gallon of cleaning solution treats 8 pails of water. So, now how many pails, to use up 16 gallons of solution?
March 25, 2015

Pre-Calculus
(s+6)^2 = 3/4 s+6 = ±√3/2 s = -6±√3/2 This is where it helps to keep track of things s = -6 ± (√3/2) NOT s = (-6±√3)/2 so, putting it all over 2, s = (-12±√3)/2
March 25, 2015

math
take a look at the number line. 29035 is to the right of 0. -1349 is to the left of 0. so, the distance between them (the difference, in other words) is 29035 - (-1349) = 29035+1349 = 30384
March 25, 2015

Algebra
that's only about 6.5 meters on a side. So, probably not elephants, nor mice. What smallish animals do you know?
March 25, 2015

math
total change: 35 degrees total time: 7 hours so, average change is 35°/7hr = 5°/hr
March 25, 2015

math
you have difficulty adding and subtracting numbers?
March 25, 2015

PreCalculus
since the area of a circular segment is a = 1/2 r^2 (θ-sinθ) you need θ such that cos(θ/2) = x/8 so, you need to solve 1/2 * 64 (2*arccos(x/8)-sin(2*arccos(x/8))) = 64π/3 x = 2.12 inches ---------------------------------- 3.5 mi/hr = 0.058 mi/min If ...
March 24, 2015

math
42 feet
March 24, 2015

math
If the 2nd piece is x, then x+3.57 + x + x+2.97 = 15
March 24, 2015

geometry
c = 2πr, so r = C/2π v = 4/3 π r^3 = 4/3 π (C/2π)^3 = 4/3 π C^3/8π^3 = 1/6 C^3/π^2
March 24, 2015

math
how about a 7-layer pyramid, with each layer 1 block wider than the layer above? Start with just 1 block on top.
March 24, 2015

math
x+y = 90
March 24, 2015

geometry
it's a frustrum of a cone.
March 24, 2015

Solid Mensuration
recall the volume of a spherical cap, as found here: http://en.wikipedia.org/wiki/Spherical_cap Now just plug in your numbers.
March 24, 2015

Solid mensuration
just look up the formula for the volume of a spherical cap of radius r and height h. Then plug in your numbers. Hint: find the volume of the smaller cap and subtract it from the whole ball. See here: http://en.wikipedia.org/wiki/Spherical_cap
March 24, 2015

math
recall that BC-AB < AC < BC+AB
March 24, 2015

PHYSICS -urgent
horizontal is constant at 92 m/s vertical is 9.8*19.9 so, (d) is just the resultant speed s, where s^2 = h^2 + v^2
March 24, 2015

Implicit Differentiation (Please HELP)
x^2 - 4y^2 + 1292 = 0 2x - 8yy' = 0 y' = x/4y You have x and y, so y' = 1/4 the line is thus y-8 = 1/4 (x-8) see at http://www.wolframalpha.com/input/?i=plot+x%5E2+%E2%88%92+4y%5E2+%2B+192+%3D+0%2C+y+%3D+1%2F4+%28x-8%29%2B8
March 24, 2015

algebra
√18/(√18-3) recall that (a-b)(a+b) = a^2-b^2. So, multiply by the "conjugate" to get √18(√18+3) / (√18-3)(√18+3) = (18+3√18)/(18-9) = (18+3√18)/9 = (6+√18)/3 = 3+√2 (4-3√2)^2 = 4^2 - 2(4)(3√2...
March 24, 2015

Math
any two points can be joined by a single line. In this case it's y-52488 = ((-393216-52488)/(-4-3))(x-3) There are many power functions which can go through any two points.
March 24, 2015

math
which is greater 8/4 or 5/3? and what do you mean by "over" when talking about paints?
March 24, 2015

Math
original size: w(w+2) after folding, the box is (w-12)(w+2-12)6 = 4050 w = 37 so, the original piece was 37x39
March 24, 2015

Math Check
How about -10x + 2y = 48 -5x - 3/2 y = -9 or, even better, -5x + y = 24 -10x - 3y = -18 or, getting rid of all the useless minus signs, 5x - y = -24 10x + 3y = 18
March 24, 2015

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