Friday
July 25, 2014

Posts by Steve


Total # Posts: 23,957

math
.12x = 104 It appears there are some broken beads, since x is not an integer. typo? If the 12% is approximate, then we can take it she has 866 or 867 beads

trigonometry
(h-1.8)/16 = tan 20°

math
His cost for 7 lbs of the mixture is 3*.60 + 2*.70 + 2*.50 = 4.20 a 25% profit requires him to charge $5.25 for that. That's $0.75/lb.

history
Sorry Civil War

history
How did the wartime economies of the North and South compare?

math
you want B/D B/D = (2/3 C)/D = (2/3 (2/3 D))/D = 4/9 A is just noise.

math
((-8+0)/2,(-6+0)/2) = (-4,-3)

history
Did sharecropping restrict the voting rights of African Americans after 1867?

Calculus Help and Check
Hmm. I thought that, using Leibniz' Rule, F'(x) = ln(8+3sinx)*cosx - ln(8+3cosx)(-sinx) Did I miss something there?

math
no idea - how big are the tiles?

math - incomplete
Do you not see that there is a lot of required information missing here?

calculus help
If you want to find F'(x) where F(x) = ∫[cosx,sinx] ln(8+3v) dv then using Leibniz' Rule, F'(x) = ln(8+3sinx)*cosx - ln(8+3cosx)(-sinx)

Calculus Help
The parabolas intersect at x = -c/2 and c/2, so we want ∫[-c/2,c/2] (c^2-4x^2)-(4x^2-c^2) dx = 256/3 4c^3/3 = 256/3 c=4 naturally, c = -4 also works

Calculus Help
the line through (3,1) and (1,8) is 7x+2y = 23 the line through (0,0) and (1,8) is y = 8x the line through (0,0) and (3,1) is y = 1/3 x So, the area is ∫[0,1] (23-7x)/2-x/3 dx + ∫[1,3] 8x-x/3 dx no sweat, eh? See the lines at http://www.wolframalpha.com/input/?i=pl...

trig
tanθ = 8/12 roughly. θ actually needs to be slightly more, because the ball falls some due to gravity. But, a little investigation should convince you that the discrepancy caused by gravity can be eliminated because of the ball's diameter, given proper conditions.

math
232mi/4hr = (232/4)(mi/hr) = 58mi/hr or, using your formula 232 = r*4 and the division proceeds from that

Trig. Math
Hmmm. If the legs are a and b, and the hypotenuse is c, then we have r = (a+b-c)/2 = ab/(a+b+c) Since A = ab/2, that means r = 2A / (a+b+c) with r=2, that means A = (a+b+c) But, since a+b+c = (a+b-c)+2c, we have A = 2r+2c A = 4+2c

MATH HELP ONLY 1 QUESTION!
Looks more like A to me.

Algebra
or, consider this as the usual work problem, where the job is to make 72 copies. 1/1.5 = 1/x + 1/2 = 1/1.5 1/x = 2/3 - 1/2 1/x = 1/6 x = 6 It would have been a little more interesting if the number of copies given for each machine had been different. You might play around with...

Geometry
well, since 4b^3+5b-3 = (2b-1)(2b^2+b+3), I think it's clear...

pre calculus
well, that'd just be 4/2 + 7i/2 = 2 + 7/2 i

calculus 1
f' = 3ax^2 + 2bx + c f'=0 at x = -2 f'=0 at x = 1 sum of roots = -1 product of roots = -2 so, -2b/3a = 1, so 2b = -3a c/3a = -2, so c = -6a f(x) = ax^2 - 3a/2 x - 6ax + d f(-2) = 3 and f(1) = 0, so 4a + 3a + 12a + d = 3 a - 3a/2 - 6a + d = 0 a=2/9 d=7/9, so f(x) = ...

pre calculus
since zt=k is constant, k=3*5 = 15, and we have zt = 15

Math 222
domains of polynomials are all reals for rational functions, exclude points where the denominator is zero. After all, division by zero is not defined.

Math (Functions)
tan -10 -sin 10 / cos -10

Trig functions
cos(kt) has period 2pi/k cos(t) has max at t=0, so -cos(t) has min at t=0 y = 4 - 2cos(pi/6 (t-15)) http://www.wolframalpha.com/input/?i=4+-+2cos%28pi%2F6+%28t-15%29%29+

Math
(-5,4) - (3,-5) = (-8,9) So, you add (-8.9) to the midpoint to get to (-5,4) So, subtract (-8,9) to get to the other endpoint: (3,-5)-(-8,9) = (11,-14)

Trigonometric Functions
as you know, a sin(k(x-h))+b has domain all reals amplitude a period 2pi/k shift h range [b-a,b+a] so, put yours into that form and read off the values

Calculus
at x, the tangent has slope 1/(2√x), so the normal has slope -2√x So, the normal line at (k,√k) is y-√k = -2√k (x-k) Since (2,0) is on that line, 0-√k = -2√k(2-k) 1/2 = 2-k k=3/2 The point is (3/2,√(3/2)) ========================...

Calculus
easy way: d = |(-4)(-5)+(7)(-5)+3|/√(4^2+7^2) = 12/√65 ============================= calculus way: the distance d can be found using d^2 = (-5-x)^2 + (-5-y)^2 = (x+5)^2 + (5+(3+4x)/7)^2 d = 1/7 √(65x^2+794x+2669) dd/dx = (130x+794) / 14√(65x^2+794x+2669...

Math
1/2 * 1/2

social studies 9
What decade did W.E.B. Du Bois write a passage about Charleston South Carolina

Math
visit calc101.com and click on the long division button. See all the details.

elective mathematics
Assuming bag2 contains 3 red and 3 white balls, P(r,r) = 5/9 * 1/2 P(w,w) = 4/9 * 1/2 so, 1/2 seems strange, no? But think. No matter what color ball you pick from bag #1, there is a 50-50 chance that the ball from bag2 will match it. If I got the ball count wrong for bag2, ju...

Math
what, no calculator? #1: 1*2*3*4*5*6*7*8*9 #2: 25*24*23

math 2
65.7 because the next digit, 3 is less than 5

Algebra 2
since loga + logb = log ab, we have log3 6(3x+1) = 2 6(3x+1) = 9 18x = 3 x = 1/6 so, how come, when I worked this out for you, assuming base 10, you didn't just follow the same steps, with a change of base?

math
3y + 2x = 3

Chemistry
mass(g) / molmass(g/mol) = moles So, for each compound, find its mol mass and divide into 100g. HNO3 has mass 1+14+3*16 = 63 So, 100g / 63g/mol = 1.59 moles Suppose I told you to find the number of bean bags in 100 lbs. You'd first have to find out how much one bean bag we...

math - typo?
Assuming the obvious typo, we have 9a+4p = 260 4a+9p = 190 which does not have an integer solution. So, maybe there's something else you need to fix.

Math logarithms
90° clockwise rotation takes (x,y)->(-y,x) so, (x,lg x) -> (-lg x,x) That is, (1/x,e^x) or (x,e^-x) enter those two functions log(x) e^(-x) at http://rechneronline.de/function-graphs/

ALG
(x+8)^2 > 0 This is true for all x ≠ -8, so (-∞,-8)U(-8,∞) (x-4) / (x-1)(x+1) <= 0 (-∞,-1)U(1,4] http://www.wolframalpha.com/input/?i=%28x-4%29+%2F+%28%28x-1%29%28x%2B1%29%29+for+-2+%3C%3D+x+%3C%3D+5

algebra
4 cups of apples

Algebra 2
log 6 + log(3x+1) = 2 log(6(3x+1)) = 2 can't tell what the base is, but if it's 10, 6(3x+1) = 100 18x = 94 x = 47/9

math
(2x)(3) = 5x - 9/4 6x = 5x - 9/4 x = -9/4

Maths
35/14 = x/18

trig
since sec^2-tan^2=1, you can multiply by that: (sec^2+tan^2)(sec^2-tan^2) sec^4-tan^4 but, since tan=sin/cos = sin*sec, that's sec^4-sin^4*sec^4 (1-sin^4)sec^4

Database Queries
I'd go with B (if you use NOT or AND) or C (if you use OR) I see no single best answer without further context. I assume you've done a web search on the phrase -- it will show lots of detailed discussions.

Help with one limit
I'd go with this: (2^n+1)/2^(n+1) = 2^n/2^(n+1) + 1/2^(n+1) = 1/2 + 1/2^(n+1) -> 1/2 as n->∞ The suggestion requires you to multiply top and bottom by 2^-n.

trig - typo
fix the typo and we can proceed from there. You can use π to copy/paste for pi.

Math
I would guess either 8/24 or 24/72 Hard to say, with no picture.

math
the circumference is 4pi the perimeter is 12 so, 4pi - 12 = ?

Trigonometry
21/x = sin 55°

4 the grade math
3/4 * 100 = 75

trig
the period is 2*6.8 = 13.6, so we have d(t) = a*cos(2pi/13.6 t) = a*cos(.462t) The max-min range is 18-9 = 9, so the amplitude is 4.5 and we have d(t) = 4.5 cos(.462t) If we call t is the hour of the day, then max is at t=6, so d(t) = 4.5 cos(.462(t-6)) Since the average depth...

algebra
you have the definition and the numbers. what do you think?

Math
35 is 17.5% of 200 So, 17.5% of 3000 = 525 as you calculated. good work.

Algebra 1 math
total possible rolls: 36 rolls that make 7: 16 25 34 43 52 61 Looks like 6/36 to me

Math
40% of the caught bears are tagged. So, 32 is 40% of what number? You are correct. It is 80.

Math
30/84 = 35.7% so, 120 is 35.7% of the population. It is indeed 336.

math
Looks like 1000 throws. Theoretical is 25% 50% 25% Empirical is 21% 48% 31%

algebra - unclear
no diagrams, and I can't see how two triangles the same height as the rectangle can enclose it.

math
7.5 hours/day * 3 records/hr * 5 days/week = 112.5 records/week per FTE So, divide that into 500 to see how many FTEs are needed.

To Damon
You are right; there's no way a 15-sided die could be fair. Even if the area of each face is the same, the angles cannot all be equal, since there is no regular 15-hedron.

Math
what situation? How much each has in savings? How much is left over after saving? How much more one has than the other at some time? when their savings are equal? If you want some help, you need to present a question.

math
Just visit calc101.com and click on the long division button. Enter your expressions and see all the details. Polynomial division is just like regular numeric long division, except that each column represents a power of x, not a power of 10. You can play around with polynomial...

Algebra
2s^2-9s+4 = (2s-1)(s-4) so the denominator is zero when x = 1/2 or 4 2s^2-5s-12 = (2s+3)(s-4) so, I guess it's clear now what the simplified quotient is, eh?

Math
You need to consider the total snowfall: 12 inches. November had 1/12 or 8.3% of the total Do the other months likewise. For a circle graph, all the sections need to add up to 100%.

Geometry
I assume "dales" means "false" consider the ostrich. It is an animal which a bird, but not a penguin. In fact, consider any bird which is not a penguin!

grade 3 math
6 * 6 4 * 9

math
What would the graph look like for the linear function of y = 1/3x -4

math
thank you

math
so, did you check the values? x-change = +2 y-change = -3 slope = -3/2

math
If X = 2 4 6 8 y = 1 -2 -5 -8 What is the slope I know that slope = vertical change over horizontal change and rise over run

math
sinx - √3/2 > 0 sinx > √3/2 you know that sin π/3 = √3/2 and sinx > 0 for 0<x<π and sin(π-x) = sin(x) So, sinx > √3/2 for π/3 < x < 2π/3 Maybe a little look-see at the graph of sin(x) would help your intu...

math - typo
fix the typo and we'll talk

calculus
what about it? (x^2-4x+6)/(x-3)^3 has asymptote at x=3 see graph and analysis at http://www.wolframalpha.com/input/?i=%28x^2-4x%2B6%29%2F%28x-3%29^3 where you can play around with other functions as you will.

CALCULUS
A. ∫[0,3] 1/√(x+1) dx = 2√(x+1) [0,3] = 2 B. using discs, v=∫πy^2 dx = π∫[0,3] 1/(x+1) dx = πlog(x+1) [0,3] = πlog4 C. We want c where π∫[0,c] 1/(x+1) dx = π∫[c,3] 1/(x+1) dx log(c+1)-log(0+1) = log(3+1)-l...

algebra 1
y=ax+b 8a+b = 345 6a+b = 265 2a = 80 a=40 b=25 y = 40x+25

Math Help!
as you know, area varies as the length squared volume varies as the length cubed. So, since weight varies as volume, look for W=kL^3 for some number k. See whether the ratios of L^3 and W are relatively constant.

math
the difference is 475 As a fraction of 1725, that is 475/1725 = 0.275 or 27.5%

math 109
500/(1+(.04)(2/3)) = 487.01

math (5)
Even if the above formula is correct, it would surely not be the correct answer, since like terms have not been combined, and the order of powers is unconventional. Also, there is no constant term, even though both P and Q contain a constant term, so there is no way it could b...

math (3)
you need s^2+t^2 >= 0 can you think of any real values for s or t where that would not hold?

Math
surely you know that the domain of √x is x>=0 so, here you have √(4-(u^2+v^2)) so you need 4-(u^2+v^2) >= 0

solid mensuration
Our nice triangle has hypotenuse length = 10. As we know, the median from C to AB is 1/2 AB, or 5. So, we now have triangle AED with legs 5 and 12, so DE = 13.

aptitude
Divided equally, X,Y,Z get 500 each Divided proportionally, X gets 4500/10000 = 45% of 1500 So, subtract 500 from that to get the difference.

Math
x+18 + x+18 + x = 54 x = 6

Calculus
P(t) = 20/(1+3e^-0.02t) = 20(1+3e^-.02t)^-1 P'(t) = 20(3e^-0.02t)(-0.02) * (-1)(1+3e^-0.02t)^-2 = 1.2e^-.02t (1+3e^-.02t)^-2 P"(t) = 1.2e^-.02t(-.02)(1+3e^-.02t)^-2 1.2e^-.02t (-2)(1+3e^-.02t)^-3 (-.06e^-.02t) which, after suitable rearranging is = 0.024e^-.02t (3e^-....

Math Urgent!
I find it helpful to use Newton's divided difference: 8030 + 21.5(x-200) + (-0.035)(x-200)(x-500) = 1/200 (-7x^2+9200x+46000) further analysis at http://www.wolframalpha.com/input/?i=8030+%2B+21.5%28x-200%29+%2B+%28-0.035%29%28x-200%29%28x-500%29

college algebra
x < 23/3

Math
5/6 = 0.83333... 4/11 = .363636... 1/13 = .076923 076923 ... Look at the length of each repeating group. Divide that into 200 to see how many repetitions there are, and what remainder. For instance 13/70 = .1857 142857 142857 ... There are 4 leading digits, so that leaves 196....

math
1/((3/4)*(2/3)) = 1/(1/2) = 2km

Math
c = 17.95 + 0.03m

math
200 + .02x = .15x

Math
pi * 25 * 6 in^3 * .2oz/in^3 = 94.2 oz

algebra I
x >= 100

Math
It hits the ground when the height is back to zero. just solve for t when h=0 use your normal methods to solve 16t^2 + 14t - 100 = 0

math
.8x = 40 x = 50

Math
#1 is correct #2 is correct, but you left out the last step: 2h/y

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