Friday

September 19, 2014

September 19, 2014

Total # Posts: 25,062

**math**

If there are x with stripe only y with dot only z with stripe and dot, z = 6 (x+z) = 3y 3(y+z) = 2x So, x+y+z = 40
*September 12, 2014*

**Algebra**

minimum cost is at the vertex of the parabola, which occurs at x = 8/(2/5) = 20
*September 12, 2014*

**Mathematica**

or, convert to have the same denominator. 1/3 = 5/15 3/5 = 9/15 9 is 5+4, or 80% more than 5
*September 12, 2014*

**Math**

(a) recall that the vertex occurs at t = -b/2a = 20/32 = 5/8 So, figure h(5/8) (b) solve for t when h=0 (c) the point where he lands is a root of the function. h(t) = 0
*September 12, 2014*

**Math**

Looks like y = -|x^3| or y = -|x|^3 Not sure what the parent function would be. |x|^3 I guess, if all modifications to be considered are linear transformations.
*September 12, 2014*

**Algebra**

only if a=b
*September 12, 2014*

**MATH**

Base b only needs b symbols. After all b are used up, the next number is 10, and the bottom digit cycles through the other b-1 digits again, before going on to 20 (assuming b >= 2!)
*September 12, 2014*

**algebra**

T F (-2)^2 = 2^2 T
*September 12, 2014*

**algebra**

1 < 3x+2 < 12 subtract 2: -1 < 3x < 10 divide by 3: -1/3 < x < 10/3
*September 12, 2014*

**Pre-Calculus/Trigonometry**

Not A. It charges double for minutes over 250 Not B. flat rate up till x=250 Not C. Drops the $29 for x>250 Clearly D. Only charges the .35 for those minutes over 250.
*September 12, 2014*

**Algebra**

PI, not pie! v = pi r^2 h + 2/3 pi r^3 So, given the numbers above, pi (225) h + 2/3 pi (3375) = 10800 pi h = (10800pi - 2250 pi)/(225pi) = 38
*September 12, 2014*

**maths**

a=2 For details using elimination, see http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
*September 12, 2014*

**trigonometry - kindly help, needed badly**

Draw a diagram, looking along the stream. If the width of the stream is w, and the height of the tree is h, then h/w = tan38°23' h/(w+200.6) = tan20°22' Eliminating w, we have h*cot38°23' = h*cot20°22' - 200.6 h = 200.6/(cot20°22' - ...
*September 12, 2014*

**Math**

Ahem 2 = Ab^-1 = A/b, so A = 2b 1 = Ab^3 = 2b^4 b = (1/2)^1/4 2 = A*2^(1/4) A = 2^(3/4) y = 2^(3/4) (1/2)^(x/4) or y = ∜(8/2^x)
*September 12, 2014*

**Grade 9 Math**

-(w^2 - 60w + 900) + 80w + 600 -w^2 + 60w - 900 + 80w + 600 -w^2 + 140w - 300
*September 12, 2014*

**Algebra Grade 10**

If we place the vertex at (0,2), then y = 2-ax^2 Since the span is 5 meters, the roots are at x = ±5/2 So, 2 - 25/4 a = 0 a = 8/25 y = 2 - 0.32x^2
*September 12, 2014*

**Math Problem (please help)**

How about 2(6*3)+2w = 36+2w
*September 12, 2014*

**Math 112**

I say see the related questions below and look at the response I posted yesterday.
*September 12, 2014*

**Maths**

consecutive angles are supplementary, so the angles are 44,136,44,136
*September 12, 2014*

**Math**

If 60% were boys, the ratio of boys:girls = 3:2 So, b/(b-1) = 3/2 2b = 3b-3 b = 3 So, 3 boys, 2 girls 60% boys
*September 12, 2014*

**Algebra**

(116 1/4) / (3 3/4) = 31
*September 12, 2014*

**Math Problem (please help)**

9x^3 - 30x^2 + 37x - 26 = 0 A little poking around with synthetic division show that f(x) = (x-2)(9x^2-12x+13) So, the only real root is x=2
*September 12, 2014*

**Math Problem (please help)**

Just solve -35x^3 + 2500x^2 - 275000 = 850000 using your favorite numeric method, or a graphing utility such as http://www.wolframalpha.com/input/?i=-35x^3+%2B+2500x^2+-+275000+%3D+850000
*September 12, 2014*

**math**

having no diagrams to consider, I'd say you did not explain anything well enough.
*September 11, 2014*

**Math**

any number between 0 and 2
*September 11, 2014*

**Math**

.00006 = 6*10^-5 I'd round up to 10^-4 789000 is almost a million, or 10^6 It is 7.89*10^5, so it rounds up to 1.0*10^6
*September 11, 2014*

**algebra**

anders-carmen = (anders-kaye) + (kaye-carmen) = 4.89 + 10 = 14.89 Rearranging things a bit, we are told Carmen finished 10 seconds before Kaye Kaye finished 4.89 seconds before Anders. alicia and donna are just noise.
*September 11, 2014*

**math**

h(t) = 51.6 - 4.9t^2 we want the time between when h(t) = 15.7 and h(t) = 1.90 So, just solve for t in 51.6-4.9t^2 = 15.7 51.6-4.9t^2 = 1.90 and subtract to find how long it will take to crush the man's skull.
*September 11, 2014*

**college math**

OK, v = 1/3 π r^2 h so, what? 3v = πr^2 h h = 3v / πr^2
*September 11, 2014*

**college math**

if x liters evaporate, the salt content remains the same, so .12(110) = .20(110-x) Now just solve for x.
*September 11, 2014*

**college math**

since distance = time*speed, 11x = 10(4.2-x) x = 2 So, the boat's speed is 2 knots. I expect now you can figure the distance.
*September 11, 2014*

**Geometry**

Nope. LM cannot be the midpoint of LM. If N is the midpoint of LM, then LN is half of LM, so 3x+5 = 2(5x+40) 3x+5 = 10x + 80 7x = -75 that makes the lengths negative. So, we must have M is the midpoint of LN. In that case, 5x+40 = 2(3x+5) 5x+40 = 6x + 10 x = 30 So, LM=MN=95 ...
*September 11, 2014*

**math**

#1: naturally, (1/4)/39.35 hours time = distance/speed
*September 11, 2014*

**Magic Square**

The sum of all the numbers is 99, so each row must sum to 33 10+11+12 = 33, so maybe that will form a diagonal. A little playing around, placing 19,20,21 in different rows and columns, gave me 19 3 11 2 10 21 12 20 1
*September 11, 2014*

**math**

p = r+4 6(r+4) + 8r = 38 So, solve for r and then figure p.
*September 11, 2014*

**Differential Equations**

Evidently you have not reviewed the definition of a linear DE: A differential equation is linear if the unknown function and its derivatives appear to the power 1 (products of the unknown function and its derivatives are not allowed) and nonlinear otherwise. So, the first ...
*September 11, 2014*

**math**

Hard to say. What is x supposed to represent? Any of the selections could be correct, depending on what x is.
*September 11, 2014*

**geometry**

For x, -9 is 8 below -1 So, the other end is 8 below -9, or -17 Same for y. The other problem is the same method.
*September 11, 2014*

**Math**

Geez. We can, without loss of generality assume that a < b, so since the parabola opens upward, it dips below the x-axis between the roots. Naturally, it changes signs at a and b. UNLESS a=b In that case, there is a single root, and the polynomial does not change sign, as ...
*September 11, 2014*

**Math**

clearly the polynomial is zero if any of its factor is zero. So, one value of x is where x-a=0, os x=a I expect you can find the other.
*September 11, 2014*

**Algebra 1**

88-7.5 <= x <= 88+7.5
*September 11, 2014*

**math**

19:7 > 7:26
*September 11, 2014*

**math**

what "result" must be 6 digits? x+y+z = 39 y = z/2 x = z-1 x=15 y=8 z=16
*September 11, 2014*

**Calculus II**

Looks good to me. I'd have just written 9/√51, but some folks get itchy over radicals in the denominator.
*September 11, 2014*

**math**

the planes are approaching at 520+620=1140 mph By the time the 2nd plane takes off, the distance between the planes is only 1800-520=1280 miles At those speeds, they cover the distance in 1280/1140 = 1.123 hours I expect you can now answer the question.
*September 11, 2014*

**math**

since time = distance/speed, d/4 + d/2 = 126 Now just solve for d
*September 11, 2014*

**math**

If $x at 4%, then .04x + .025(14000-x) = 458
*September 11, 2014*

**math**

The new machine completes 2/13 of the job. So, the older machine requires (11/13)/(1/15) = 12.7 hours to do the rest.
*September 11, 2014*

**math**

Hmmm. I may have been hasty. Anyway, if there are x oz. of $3.50 alloy, the rest (30-x) is the $7.00 alloy. So, check to be sure that the value of silver adds up: 3.50x + 7.00(30-x) = 6.30(30) x = 6
*September 11, 2014*

**math**

we've done a lot of these mixture problems for you. Why not try some yourself, and we can check your work...
*September 11, 2014*

**Math**

Do you not see that you are missing some data here?
*September 11, 2014*

**math**

Tell you what. I'll solve one, and you can try the others. Post your work if you get stuck. x^2-3(2x+3)=0 x^2-6x-9 = 0 x = (6±√(36+36))/2 = (6±6√2)/2 = 3±3√2
*September 11, 2014*

**Grade 10 Maths**

recall that the vertex of a parabola is at x = -b/2a In this problem, that is x = -20/-1 = 20
*September 11, 2014*

**1**

First, find the speed of sound, and then recall that distance = time * speed. Then, since time = distance/speed, divide that distance by the speed of light.
*September 11, 2014*

**Year 10 Alegbra**

A = 8w - 2w^2 As you recall, the vertex of a parabola (in this case, the maximum area) is achieved at x = -b/2a In this case, that's x = -8/-4 = 2 Or, you can note that the roots of A=0 are 0 and 4. The vertex is midway between the roots, at x=2.
*September 11, 2014*

**Year 10 Alegbra**

depends on what the question is, no?
*September 11, 2014*

**math**

so, you gonna share those roots with us?
*September 11, 2014*

**Math: pre calculus**

If the width of the pens is x, and the overall length is y, then 3x+y = 240 The area is a = xy = x(240-3x) = 240x - 3x^2 This is just a parabola, with vertex at x = 40 So, the pens are each 40 by 60 ft. As usual, maximum area is achieved when the available fence is divided ...
*September 11, 2014*

**mathematics**

just as x^a * x^b = x^(a+b) log(a*b) = log(a) + log(b)
*September 11, 2014*

**MATH**

ummm, 53x5 = 265
*September 11, 2014*

**Force of Gravity**

since F = GMm/r^2 when r doubles you have GMm/(2r)^2 = Gmm/4r^2 = GMm/r^2 * 1/4 = F/4
*September 11, 2014*

**Geometry**

we have if p then q we are told p is true, so therefore, q: the measure is 90 degrees.
*September 11, 2014*

**8th Grade math**

False who says they have to be spaced 1 degree apart? If they are spaced 1 minute apart, there are 60*360 = 21,600 rays
*September 11, 2014*

**Quantitative Reasoning (math)**

360/60 = 6
*September 11, 2014*

**8th grade math**

Nope.
*September 11, 2014*

**8th grade math**

False. Between any two points there is another. Following that reasoning, between any two points there are infinitely many others.
*September 11, 2014*

**Math**

The 10x10 cake is 5x5 pieces, so it takes 4+4=8 cuts to do the job. That is 5 seconds per cut. The 12x12 cake is 6x6 pieces, so it will take 5+5=10 cuts, or 50 seconds. Assuming a 12" cut can be made in the same time as a 10" cut!
*September 10, 2014*

**Math**

If the original selling price was s, then she paid 3*s(1-.20)+10
*September 10, 2014*

**Math**

If there were originally b boys out of s students in the class, b/s = 2/3 b/(s+2) = 3/5 Or, b = 2s/3 5b = 3s+6 So, 5(2s/3) = 3s+6 10s = 9s+18 s = 18 Now you should be able to answer the question.
*September 10, 2014*

**pre calculus**

You know that a parabola with vertex at (h,k) is y = a(x-h)+k So, we now have y = a(x+3) - 10 Now just plug in (2,-5) to find a.
*September 10, 2014*

**Geometry**

Now you know that RSP = PST = -17 So, since RST = RSP + PST, RST = -34 Not sure what the negative values indicate. Sure there's not a typo in the problem?
*September 10, 2014*

**Geometry**

Use your distance formula: AB = √((2-0)^2+(7-3)^2) = √(4+16) = √20 = 2√5
*September 10, 2014*

**math**

Actually, the volume of a cone is v = 1/3 π r^2 h
*September 10, 2014*

**math**

2(w + 2w-3) = 144
*September 10, 2014*

**Math**

1,2,3,4,5,6,7,8,9,10,11,12,13 add up to 91. So, it looks like we have 1,2,3,4,5,6,7,8,9,10,11,12,14
*September 10, 2014*

**math**

Not quite sure what you're doing there. If a side of the square is 45, its perimeter is 180. Thus, the perimeter of the triangle is 90. So, each side of the triangle must be 30.
*September 10, 2014*

**algebra 1**

If x >= 0, |x| = x If x < 0, |x| = -x So, from what we have above, x >= 0 x-2 < 0, or x < 2 So, 0 <= x < 2
*September 10, 2014*

**Trig**

If the nearer observer is at distance x from the obelisk, then we have h/x = tan 65° h/(x+25) = tan 44° so, eliminating x, just solve for h in h/tan65° = h/tan44° - 25 h = 25/(cot44°-cot65°)
*September 10, 2014*

**math**

400m / 92s = 4.35 m/s or, 400m / 1.533 min = 260.9 m/min
*September 10, 2014*

**college algebra**

If x oz. of 1% are used, then the rest (3-x) are 5%, so .01x + .05(3-x) = .04(3) x = 3/4 So, 3/4 oz of 1% and 9/4 oz of 5% Note that 4% is 3/4 of the way from 1% to 5%, so 3/4 of the total is the 5% strength.
*September 10, 2014*

**college algebra**

If x is at 8%, the remainder (22000-x) is at 6% so, .08x + .06(22000-x) = 1680 ...
*September 10, 2014*

**math**

just plug in your numbers: h(t) = -16t^2 + 84t + 60 assuming he kicks it straight up. Now just plug in t=2
*September 10, 2014*

**Math**

Since A+B+C=180, C=94.24 So, using the law of sines, c/sinC = a/sinA Now just plug and chug.
*September 10, 2014*

**Algebra!!!! HELP**

Since F=kx, F/x is constant. So, (a) 120/x = 265/0.15 (b) F/0.3 = 265/0.15 Note that you can answer these questions without even determining the value of k explicitly.
*September 10, 2014*

**math**

Just use the quadratic formula: x = (-(c-a)±√((c-a)^2 - 4(b-c)(a-b)))/(2(b-c)) You can play around with that some, but I don't see much in the way of simplification. http://www.wolframalpha.com/input/?i=%28b-c%29x%C2%B2+%2B+%28c-a%29x+%2B+%28a-b%29
*September 10, 2014*

**math**

(6x+2)/4 + (2x²-1)/(2x²+2) = (10x-1)/4x Clear fractions by using the common denominator of 4x(x²+1). This requires that x≠0. (6x+2)(x(x²+1)) + (2x²-1)(2x) = (10x-1)(x²+1) (6x^4+2x^3+6x^2+2x) + (4x^3-2x) = (10x^3-x^2+10x-1) 6x^4 - 4x^3 + 7x^2...
*September 10, 2014*

**calc**

If you found T(t) = r'/|r'|, then you should be able to get N(t) = T'/|T'| Where do you get stuck?
*September 10, 2014*

**math**

(1) 2(x + x-3) = x(x-3) x = 1 or 6 But x=1 isn't viable, so only x=6 (2) 2(x+x) = x^2 x = 4
*September 10, 2014*

**maths-calculus**

If you let u = -(x+1), you have u(e^(-1/u) - 1) = (e^(-1/u) - 1) / (1/u) Now using l'Hospital's Rule, that is the same as (e^(-1/u) - 1)(1/u^2) / (1/u^2) = e^(-1/u) - 1 -> 0-1 = -1
*September 10, 2014*

**Math**

I'd say -40 + 20 = -20
*September 10, 2014*

**math**

sounds like a good deal. Was there a question in there somewhere?
*September 10, 2014*

**math**

Since the density is obviously 2 seedlings/hill, I suspect you want the density in terms of seedlings/m^2 or something. Since each hill occupies 400cm^2, the density is 2 seedlings/400cm^2 = 1/200 seedlings/cm^2 Maybe not too useful. In terms of m^2, that will come out 2 ...
*September 10, 2014*

**programming**

Can you see what a useless question that is to be asking here? Any exposition you find here will only be what you can find in your text (if any) or in any of the sites turned up by google.
*September 10, 2014*

**math**

If Stevie sings x songs, then Christine sings x-6 songs. Add them up: 8 + x-6 + x = 18 x = 8
*September 10, 2014*

**Math!!**

yes. good job.
*September 9, 2014*

**Math**

You have an arithmetic progression where a = 20 d = 4 T20 = 20+19*4 = 96 S30 = 30/2(2*20+29*4) = 2340
*September 9, 2014*

**math**

8+(7) = 8+7 = 15
*September 9, 2014*

**mathematics**

In order to guarantee any reds at all, you need to draw 41, since the first 40 might be all green and white. So, 45 draws will guarantee 5 reds.
*September 9, 2014*

**Pre-Calculus**

easy. Just -5 to x and -4 to y: (-2,1) -> (-7,-3) and similarly for the other points.
*September 9, 2014*

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