Friday
April 18, 2014

Posts by Steve


Total # Posts: 21,739

Math
well, just evaluate 15*14*13 / 1*2*3

engineering mathematics 1
you have 2x+y=80 and you want the maximum area, a = xy = x(80-2x) find the vertex of that parabola for max area. You will find that the fence is equally distributed among the lengths and widths. That is, 2x = 40 y = 40 so the max area pen is 20x40

math
the quotient is always less than the dividend

Math
subtract and you have 7y = -14 y = -2 now plug that into either equation to find x = -3

Math
working all those words into numbers, we have maximize m+r subject to 10m + 15r <= 500 25m + 15r <= 600 I see that we have 15m <= 100 so m <= 6 Given that, if we choose only 1 mouse, we have 15r <= 490 15r <= 575 so, r <= 32 max achieved at 6 mice and 29 r...

Algebra
If using x lbs of 4% milk, .04x + .30(200-x) = .08(200)

math
what, you have no idea how to list multiples of 4? How about I illustrate with multiples of 3? 3,6,9,...

Math
the value of the coffee in each part must add up to the whole. So, 7.50x + 9.50(12-x) = 8.00(12) x = 9 so, 9 lbs at $7.50 and 3 lbs at $9.50

Algebra
cross multiply to clear the fractions and you have (x+12)(x+8) = x(x+4) x^2+20x+96 = x^2+4x 16x = -96 x = -6

:-)
Yeah, I sometimes have to step back and ask myself what it would take for the problem to make sense. It's not always possible to come up with an answer, either!

Math 4
It lowered the temp by 27°, not to. 19 - 27 = -8

Math 3
From the context, I gather the day temp is 107° and the night temp is -153°. 107 - (-153) = 310° warmer by day than by night.

Math 2
or, more generally, 124 - (-21) = ? If a < b, the difference between a and b is b-a.

Math 221
The given line has slope -3 So, the parallel line also has that slope. Now you have a point and a line, so the equation is y-5 = -3(x+1) y = -3x+2 Your first line was okay, but then you started dropping x's along the way. x1 = -1, not 1.

math
yes, it's 1/5 for each marble. So, the chance of getting BOTH greens is 1/5 * 1/5 = 1/25

math
2 greens out of 10 marbles, so: (B)

math
(60-25.5)/2 = 17.25

Calc
same as last time, only use the quotient rule: g = 5x/f, so g' = (5f-5x*f')/f^2 g'(3) = (5*4-15*3)/4^2 = -25/16

Calculus
g' = 8f + 8x * f' g'(3) = 8f(3) + 24*f'(3) = 8*4 + 24*5 = 152

Math
Did you try using h(t) = -16t^2 + 128t ???

Math
(a) correct. (b) correct (c) correct (d) max height is at t=4. But the question was, what is that height? h(4) = 256 No idea how to graph it with your calculator. The graph can be seen at http://www.wolframalpha.com/input/?i=-16t^2%2B128t

Algebra
If he intended to buy x dozen, the price was evidently 210/x cents/dozen. Instead, (x-1/2)(210/x + 3) = 209 x = 6 So, the price per dozen was expected to be $.35 Instead, he wound up paying $.38/doz, meaning he bought 5 1/2 dozen, which cost $2.09

Physics
(1500cm^3)/(1.0s) / (pi*(.49/2)^2 cm^2) = 7954 cm/s or 7.9 m/s not sure on B.

Math (2 Questions) - Please Help
F+V-E = 2 If you count all the vertices of each polygon, each vertex is counted twice. So, 12+20 + (5*12+6*20)/2 - E = 2 E = 120 draw a diagram. If you draw horizontal and vertical lines through the point and through the center of the circle, you will see that (r-25)^2 + (r-18...

Algebra
the function is undefined when you try to divide by zero. So, if b+4=0, the function is undefined.

Math- urgent
the obvious one is -265:100 also 53 : -20

gg
that would be 125000(.27) = $33,750

Math
solve for t in 6 + 31t - 16t^2 = 4 t = 2

Trig
use law of cosines. 70^2 = 65^2 + 90^2 - 2(65)(90)cosθ

college math
Sounds like they are repeatedly doing surveys. In most of the surveys (19/20), they sample enough of the population to be confident that their results are within 3.2% of the true percentage.

CALCULUS
with a slight change to the numbers, this question is treated at http://www.jiskha.com/display.cgi?id=1392927547

Algebra
not sure what you want to do. If you just want to do long division, visit calc101.com and click on the "long division" button. Enter your polynomials and see all the details.

5TH GRADE MATH
If you mean that the sum of the three perimeters is 140 yards, then you can divide 140 up any way you like. If you pick, say, 30,50,60 yards as your three perimeters, then you can divide the values up as you will. For example perimeter 30: 7x8 yards perimeter 50: 25 ft by 50 f...

Mathematics
P is in QI, so if cosP = 5/13, tanP=12/5 Q is in QIII, so if tanQ = 8/15, sinQ = -8/17 17tanPsinQ = 17(12/5)(-8/17) = -96/5

trigonometry
h/63 = sin 45

calculus help
There's a nice discussion here: http://math.stackexchange.com/questions/126755/lhospitals-rule-with-indeterminate-powers

Math
to figure a percentage, just divide and multiply by 100. 2023.60/55953.77 = 0.0361 = 3.61%

Calculus Help!!!!!
should be no problem. That's just Algebra II. Anyway, y = x^3/(x+1)^2 y' = x^2(x+3)/(x+1)^3 y" = 6x/(x+1)^4 see the graph and some analysis here: http://www.wolframalpha.com/input/?i=x^3%2F%28x%2B1%29^2

Precalculus
You have (tan+sec-1)/(tan-(sec-1)) multiply top and bottom by tan+sec-1 and you have (tan+sec-1)^2/(tan^2-(sec-1)^2) tan^2+sec^2+1+2tan*sec-2tan-2sec)/(tan^2-sec^2+2sec-1) (sec^2+tan*sec-tan-sec)/(sec-1) (tan+sec)(sec-1)/(sec-1) tan+sec

Calculus Help Please!!!
As mentioned, let BC = x distance over water: √(x^2+49) distance over land: 11-x (a) energy expended: y = 1.3√(x^2+49) + 11-x dy/dx = 1.3x/√(x^2+49) - 1 y'=0 at x = 70/√69 what do you get for the other parts?

algebra
you just have a right triangle with legs 5 and 8. So, the rope, forming the hypotenuse is √(25+64) = √89

Calc 2
and the (-2/3)^k part is just a geometric series S = (-2/3)/(1+2/3) = -2/5

geometry
x^2 + 6371^2 = (6371+353)^2 x = 2150

Algebra
2 hours

Math
√(25^2 + 10^2)

math
(P2-P1)/P1 * 100

Calc
dQ/dt = kQ (if you please)

CHEM
since PV/T is constant, if P is held constant, then V/T is constant. if T is increased by a factor of 296/90, then V is increased by a factor of 296/90. So, multiply 3.3 by that factor.

math (Matrix algebra)
Enter your data at http://www.gregthatcher.com/Mathematics/GaussJordan.aspx to see all the details

math (Matrix algebra)
assuming you mean a determinant, and calling your matrix M, I get |M| = 31-3x So, if 31-3x = 25, x=2 The inverse can be seen at http://www.wolframalpha.com/input/?i=inverse+{{-2%2C+1%2C+x%2B2}%2C{3%2C+x-4%2C+5}%2C{0%2C+1%2C+3}}+ substitute in x=2 if you just want the numbers.

maths
since one line is slanting, and the other is horizontal, I'd say they are not parallel. Even is there's an x missing from the 2nd line, it will still not be parallel.

maths
x y -4 13/2 -3 5 -2 7/2 ...

Algebra
since time = distance/speed, we have 5/x + 5/(2x) = 15/(2x)

Math
5% growth is just 1200000*1.05^n after n years for #c, we have 1200000*(1.05)^7*(0.92)^8 = 866,581

Algebra
x^2+8x+15 = (x+3)(x+5) so, you have (x+3)(x+5)/(x-4) * (x-4)(x+4)/2(x+3) the x+3 and x-4 cancel, leaving (x+5)(x+4)/2

math
out of 36 possible rolls, only 4 have the sum < 5: 12 13 21 22 What's the chance of no 6's? 5/6 * 5/6 so, take 1-P(~6,~6) = 11/36

Algebra
the point of Reiny's question is to remind you that division by zero is undefined. So, when b+4=0, the expression cannot be evaluated. That is, when b = -4, the expression is undefined.

Math
I get zero. ∫[-1,2] 1-x^2 dx = x - x^3/3 [-1,2] = (2 - 8/3) - (-1 + 1/3) = 0 yeah, I know, we have to divide by 3 ...

Trig - heh
now, just change all those 225's to 255's and redo the calculations.

Math
PR/QR = sin(Q) PR/120 = sin(10.5)

Calculus Help Please Urgent!!!
1/3 pi r^2 h = 30, so h = 90/(pi r^2) surface area = 2 pi r s where r^2+h^2 = s^2, so a = 2 pi r √(r^2 + (90/(pi r^2))^2) = 2/r √(pi^2 r^6 + 8100) for minimum paper, we need da/dr = 0, so, as wolframalpha so ably shows at http://www.wolframalpha.com/input/?i=2+pi+r...

mathematics for management
5^x 25^2y = 1 5^x 5^4y = 1 5^(x+4y) = 1 x+4y = 0 3^5x 9^y = 1/9 3^5x 2^2y = 3^-2 5x+2y = -2 x = -4/9 y = 1/9

math
Assuming you mean (8^y)^y, we have 8^y^2 = 2^3y^2 1/32^y = 2^-5y 4 = 2^2 3y^2-5y = 2 y = 2 or -1/3

mathematics for management
2log(a+b) = log (a+b)^2 = log (a^2+2ab+b^2) 2log a + log(1 + 2b/a + b^2/a^2) = log (a^2 (a^2+2ab+b^2)/a^2) looks the same to me

math
Assuming a 360-day year, 8000 * .095 * 1/3 = 253.33

math
ignoring all those trailing zeros, 58/6 = 9.67

calculus
1/10 ∫[0,10] 3/(x+1) dx = 3/10 ln(11)

math
the bisector BD and half the chord CD form a right triangle with the radius BC BC^2 = 3^2+5^2

math
the one with an x term, but no higher powers.

calculus
So, the height is 40/x^2 c(x) = 2x^2*5 + 4x(40/x^2)*2 = 10x^2 + 320/x set the derivative to zero, and you find minimum cost at x = 2∛2

Precalculus
for #2c, there is a second point at about (-1.38,3) see the graph at http://www.wolframalpha.com/input/?i=solve+5x^3-3x^5%2B1+%3D+3

statistics
C

cal
false. These are formulas for interest compounded k times per year.

math
have you tried your calculator?

Math
850000(1+.06/4)^(4*3.5)/4.75 = 220,419 850000(1+.06/4)^(4*5)/5.10 = 224,476

statistics
well, who has a negative z score?

Math
As I showed you earlier, it is ∫[0,8] 7/(x+1) dx ---------------------- (8-0) = 1/8 (7log(x+1) [0,8]) = 7/8 (log9-log1) = 7/8 log9 what were your solution steps?

Algebra
(r+2)/(r+4) - 3/(r+1) = (r^2-10)/(r^2+5r+4)

math
5n + 25q = 325 q = n-5 now just plug in q and solve for n.

Algebra
1/(g+2) + 3/(g+1) = (4g+7)/(g^2+3g+2)

Math
using FOIL, you get (2n)(6n) + (2n)(1) + (2)(6n) + (2)(1) = 12n^2 + 2n + 12n + 2 = 12n^2 + 14n + 2

math trigonometry
the law of cosines says 68^2 = 53^2 + 71^2 - 2*53*72 cosθ so, cosθ = (68^2-53^2-71^2)/(-2*53*72) = 0.42269 θ = 65°

Algebra
the common denominator is 2b, so you have 1/2b + b^2/2b = (1+b^2)/2b

Math
and there's your answer.

Math
17 is 17*1 so, what is 17*23.125?

Mean, Median and Mode HELP!
sort the data to get 4 6 7 9 10 11 11 12 15 16 Now it is easy to see mode = 11 median = 10.5 mean = 10.1

Math
distance is ∫[0,8] 3t√(640t^2) dt = 512

Math
that would be ∫[0,3] 300t^2/(t^3+32) + 5 dt let u = t^3 + 32 du = 3t^2 dt and now you have ∫[32,59] 100/u du + ∫[0,3] 5 dt = 15 + 100log(59/32)

Math
∫[-1,2] 1-x^2 dx ----------------------- (2-(-1))

Math
∫[0,8] 7/(x+1) dx ---------------------- (8-0)

Math
that would be (∫[0,8] 5e^-x dx)/(8-0) = 5/8 (1-e^-8)

Algebra
since the denominators are equal, just subtract the numerators: ((5x-2)-(x-2))/(4x) = (4x)/(4x) = 1

trying to understand math
in March, total sales were 9.00 * 125 * 31 = 34875.00 In April, (assuming 30 days, 15 days per half-month) 1st half: 9.00*125 * 15 = 16875.00 2nd half: 11.00*125 * 15 = 20625.00 total: 37500 avg at 11.50 = 43125 so she falls 5625 short. Two items need clarification... There...

math
(pi * .8^2 * .5 m^3) ----------------------- = 32 s (pi * .1^2 * 1 m^3/s)

Algebra
just solve your equation: x^2-81 = 115 x^2 = 196 x = 14 so, the base is 14+9 = 23 height is 14-9 = 5

Algebra
√(5x^2)+7x+2-√(4x^2+7x+18) = x-4 √(5x^2)-√(4x^2+7x+18) = -6x-2 now square both sides to get (5x-2) - 2√(5x^2)(4x^2+7x+18) + (4x^2+7x+18) = (6x+2)^2 4x^2+12x+16 - 2√(20x^4+35x^3+90x^2) = 36x^2 + 24x + 4 √(20x^4+35x^3+90x^2) = -16x^2-6x+...

algebra 1
both correct However, I'd have written #2d as (5x+2 + 3x-1)/2 just to show it's the average of two numbers, rather than half of each.

algebra1
looks like A to me

College Cal 1
if the 2-strand dimension is x, then we have f(x) = 2x + x + 2(15000/x) df/dx = 3 - 30000/x^2 min fence when df/dx = 0, at x = 100 so, the field is 100x150 as usual, the fencing is divided equally among the dimensions. ** f(x) = fencing(x) !

alg
since f(1) = 5, f-1(5) = 1

Pages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | Next>>

Search
Members