Wednesday
July 30, 2014

Posts by Steve


Total # Posts: 24,023

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

Algebra
cancel 2x top and bottom 2x(x+3) / 2x(5x^2) (x+3) / 5x^2

Math
√250j^4o^5 factor out perfect squares √25√10√j^4√o^4√o now extract the square roots of the squares 5j^2o^2√10o Now you know whey o is seldom used as a variable name...

Math-Clarification
√p = -1 has no solutions. √4 = 2, not +2 or -2. squaring both sides to give p = 1 gives an extraneous solution, because √1 = -1 is not true. √1 = 1

geometry
Not sure. If the large rectangle is 7x3, then it's no sweat, since 7x3 = (2+5)x3

Math
since distance = speed * time, we need x(3+2) = (x+42)(2) x = 28

Math
a: wrong units. 3125 m^3 b: ok c: tanθ = 50/25 that's not 45° consider the diagonal of the rectangular bottom and the end of the pool. The z-axis does not matter.

math
if the depth of each hemisphere is 1, the that is also the radius. a) you know how to find the volume of half a sphere, right? b) same for surface area c) the flat area of the top of the tray is 12x12 minus the area of 12 circles with radius 1. Now add on 12 hemispheres for th...

CALC 2
the paths should not be too hard to sketch. Eliminating t, we have y = 3x-1 x = 4(y-1) - (y-1)^2 http://www.wolframalpha.com/input/?i=plot+y+%3D+3x-1%2C+x+%3D+4%28y-1%29+-+%28y-1%29^2+ now (b) and (c) become easy, though you should probably work on them using the parametric eq...

Math
no experience with Venn diagrams? The numbers are for disjoint sections of the diagram, so there's no overlap. They add up to 26, meaning that 4 students fit none of the categories. No idea whether the choice to eschew the cookies (rather than chewing them) was because the...

Math
6/10 = x/15 since 15 is 3/2 as big as 10, you want a number which is 3/2 as big as 6.

All subjects
Just google good study habits and I'm sure you will come up with lots of ideas. Heck, you might also consult your teachers and college counselor.

math (2)
well of course the lines x=2 and x=-2 do not intersect; they are parallel vertical lines. Not sure what that has to do with anything; the just set bounds to the region. Since y is an odd function, and the bounds are symmetric about the y-axis, the integral will be zero. Let u ...

maths
5/9 x = 1/2 x + 5 Now just solve for x

Calculus
using discs, we have v = ∫[0,∞] πe^(-2x) dx = π/2

math
figure the area of the pond Add 2 to the radius and figure the new area subtract the smaller from the larger.

AlgebraII( Probability)
probability = 0 if considering all real numbers. I suspect that your set of candidates has some restrictions, no?

Precalculus
From the help I've seen given on this, you should not still be having troubles. That said, however, A = {2,3,5,7,11,13} B = {1,2,3,4,6,9,12} C = {4,8,12,16} (A∩B) = {2,3} (A∩B)' = {1,4,5,6,7,8,9,10,11,12,13,14,15,16} (A∩B)'∩C = {4,8,12,16} N...

GEOMETRY !
as usual, v = 1/3 Bh = 1/3 * 230^2 * 146.7

math
just express the words in symbols: (36-4) * (36-4)/2 * 12 / 8 = 768

math
In that csae, it's the 4th value above. The 17's just cancel.

math
not sure what the expression is. If subtracting, 17*(93-97) If adding, 17(93+97) If multiplying, 17^2 * 93 * 97 If dividing, 93/97

physics
A highway is made of concrete slabs that are 14.0 m long at 20° C. (a) If the temperature range at the location of the highway is from -17.8° C to +40.8° C, what size expansion gap should be left (at 20° C) to prevent buckling of the highway? (b) How large are ...

Physics
Calculate the number of H2O molecules in a human body of mass 65.9 kg. Assume that, on average, water makes up 62% of the mass of a human body. (Use 1.0 u for the atomic mass of hydrogen, and 16.0 u for the atomic mass of oxygen.)

math - typo
oops. 2√2 left over from when I only did 1 times the area of the triangle. Ignore it.

math
√(2* 1/2 * 4pi * 4/pi) = 2√2 = 4

math
just figure the distance between the points. That is the length of the diameter. Half of that is the radius. Now figure the area of the circle.

math
You have a formula for finding d, given n. You are given d, so you need to find n. (n^2-3n)/2 = 90 n^2-3n = 180 n^2 - 3n - 180 = 0 (n-15)(n+12) = 0 n = 15 or -12 -12 is not a reasonable answer, so n=15 is the solution.

math
just plug in d=90 and solve (n^2-3n)/2 - 90 = 0 quadratics are easy, right?

GEOMETRY
I guess an Egyptologist can answer that. Maybe the typos and syntax have garbled the question.

Linear algebra
Judging from what wolframalpha gets at http://www.wolframalpha.com/input/?i=solve+x+%2B%28+a+%2B+1+%29y+%2B+a^2+z+%3D+a^3%2C+%28+1+-+a+%29x+%2B%28+1+-+2a+%29y+%3D+a^3%2C+x+%2B%28+a+%2B+1+%29y+%2B+az+%3D+a^2 I suspect a typo.

Algebra 1
#1 correct. 900P30 is the simplest possible answer. Trying to evaluate it does not add much to understanding the value of the answer. Suffice it to say that 2.6*10^88 is pretty big. #2 ok #3 ok 50C5 - combinations, since the order of their selection does not matter.

GEOMETRY
since 60 is 1/6 of 360, the mouth is 1/6 of the circle. You now have just 5/6 of the circle. I'm sure you know how to find the area of 5/6 of a circle, no?

Math - ill posed problem
Today's date keeps changing, and if you are calculating days elapsed, you cannot just say "June 2008" for the start date.

physics
the distance fallen at time t seconds is 4.9 t^2 meters I leave it up to you to discover how high the tower is, and just what you mean by "position."

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