Friday
May 6, 2016

Posts by steve

Total # Posts: 40,219

Science
change in speed over time. So, (70-15)m/s / 10min = 4.5 m/s/min Most people feel more comfortable with just two units, so that would be 4.5/m/s/min * 1min/60s = 4.5/60 = 0.075 m/s^2
March 13, 2016

science computer
max = 0 maxname = "" for i=1 to 10   read name,age   if age > max then     max=age     maxname=name   end if next i print "The oldest person is ",maxname
March 13, 2016

algebra
enter your coefficients at the URL below and see all the details. http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
March 13, 2016

Math
since the balls are replaced, the draws are independent events. Just multiply all the probabilities: 5/10 * 3/10 * ...
March 13, 2016

Math
If A's speed is a, then B's speed is a+1 since time = distance/speed, 480/(a+1) = 480/a - 40 a = 3 m/s
March 13, 2016

math
P(t) = -3400 + (4900-(-3400))/4 t = -3400 + 83.25t
March 13, 2016

math
draw a diagram. Review the cotangent function. Then you will see that if the cliff has height h feet, h cot42° - h cot54° = 15
March 13, 2016

Algebra
well, you have 7x = 3y y = 7/3 x 7/3 is the constant of variation. when one says y varies directly with x, it means that there is a constant k such that y = kx If y varies inversely as x, then there is k such that xy = k or, y = k/x These can be combined, so that if you hear y...
March 13, 2016

science
well, since no mass is lost, ...
March 13, 2016

Algebra
y = 1/4 x
March 13, 2016

math
2/5 x - (5/7)(2/5 x) + 62 = x x = 70
March 13, 2016

Trig
AD/sin75° = 100/sin65° AD = 106.58 CD^2 = 50^2 + 106.58^2 - 2*50*106.58 cos50° CD = 83.72 Hmmm. we're close. Better check (a) my math (b) your math On part b, ya got me. what are α and β supposed to be? Maybe they are to be substituted for the actual ...
March 13, 2016

Maths
5a - 5b = 100
March 13, 2016

maths
fix your typos.
March 13, 2016

Math
v varies as r^3. 729 = 9^3.
March 13, 2016

maths
59 = 2+19d Now you can find d. 6th from the end is T15 = 2+14d.
March 13, 2016

math
a = πr^2 + 2πrh so, plug in r=14 and h=35 and do the math.
March 13, 2016

Calculus
f(x) = x^(3/4) df = 3/4 x^(-1/4) dx so, if we let x=27 and dx = -0.02, df = (3/4) 27^(-1/4) (-.02) = -.00658 So, f(26.98) ≈ f(27) - .00658 = 11.84467 - 0.00658 = 11.83809 f(26.98) is really 11.838085
March 13, 2016

calculus
I guess, looking at the graphs at http://www.wolframalpha.com/input/?i=plot+y^2%3D4x,7y%3D2x%2B20,2x%2B3y%3D0 that you want the triangular-ish region with vertices at (-3,2), (4,4), (0,0) It looks like horizontal strips will be easiest to use, so the area is ∫[0,2] (y^2/...
March 13, 2016

math
That would be 10C7 (-1)^7 x^3 2^7 = -15360x^3
March 13, 2016

Math
200(1+.035n) = 221
March 13, 2016

math
(125-81.25)/125 = 0.35 = 35%
March 13, 2016

math
if each side is s, then 10/s = sin41
March 13, 2016

ALGEBRA
well, plug in the numbers is it true that -2 = (-2/3)*6 ?
March 13, 2016

Math
x + 2x = 3x tan (x+2x) = tan 3x (tan x + tan 2x) / 1 - tanx.tan2x = tan3x (tan x + tan 2x) = tan3x(1 - tanx.tan2x) (tan x + tan 2x) = tan3x - tan3x tan2x tanx tanx + tan2x - tan3x = - tan3x tan2x tanx tan3x-tan2x-tanx = tan3x tan2x tanx
March 12, 2016

Calculus
you want the tangent to have slope -1/2 y' = x/√(x^2+3) so, where is that = -1/2 ? Get the point and use the point-slope form of the line.
March 12, 2016

math
100/40 = 2.5 times as many days. So, you want to have 30/2.5 soldiers.
March 12, 2016

Math
h/m = 0.95 So, you want to solve h/40 = 0.95
March 12, 2016

Statistics
hmmm. The only other candidate I see would be 4 times that. You know P(only 1st) + P(only 2nd) + ...
March 12, 2016

Statistics
would that not be .16 * (1-.16)^3 ?
March 12, 2016

Algebra
don't know how many legs each kind of animal has? 4c+2g = 42
March 12, 2016

math
angles BAE and DEA are alternate interior angles, so m∠DEA=70°. AD=AE, so ∆DAE is isosceles. That means m∠ADE=70°. m∠DAE is thus 180-70-70 = 40°
March 12, 2016

MATH
c = (2/6)n ... There is no rate of change. It's a unit rate.
March 12, 2016

college math
just divide... 1.998x10^27 --------------- 5.688x10^23 = (1.998/5.668)x10^(27-23) = 0.3525x10^4 = 3.525x10^3
March 12, 2016

Geometry
you need to know either (a) the scale factor. The ratio of sides is the same (b) the lengths of two corresponding sides. Just divide one by the other to get the ratio (c) the ratio of their areas. The ratio of sides is the square root of that ratio.
March 12, 2016

math
wholesaler's printed price: p retailer's cost: 0.85p price after markup: 0.85p*1.10 = 0.935p price after buyer discount: 0.935p * 0.95 = 0.88825p buyer pays .88825p*1.08 = 451.44 So, p = 470.59 price/cost for retailer is .88825p/.85p = 1.045 so he made 4.5%
March 12, 2016

Math
a + a+3d = 2 a^2 + (a+3d)^2 = 20 you will get two solutions.
March 12, 2016

Algebra
2010 is 10 years after 2000, so the model predicts a population of 6084e^0.12 = 6859.69 That's overestimating by 6.69, or about 0.0976% I guess you'd need to study some on actual population trends to see whether you expect the model to remain close to the reality.
March 12, 2016

maths
draw a diagram. Draw a radius to each end of the chord. Draw a radius which bisects the chord. Now you have two 5-12-13 right triangles.
March 12, 2016

math
using discs, v = ∫[0,2] π(R^2-r^2) dx where R=4 and r =y=x^2 using shells, v = ∫[0,4] 2πrh dy where r=y and h=x=√y
March 12, 2016

math
using discs, v = = ∫[a,b] π(R62-r^2) dx where R=f(x) and r=g(x) using shells, it gets a lot trickier, because we have to idea of the behavior of f and g in the interval.
March 12, 2016

math
Let's use a little symmetry here. So, we have the base with length 2x and height x√3. That means if we add up all the thin slices, the volume is v = ∫[0,8] (1/2)(2x)(x√3) dy = ∫[0,8] √3 x^2 dy But x^2 = 8y, so v = ∫[0,8] 8√3 y dy ...
March 12, 2016

Calculus
Oops. ln(T-A) = -kt + ln(c) T-A = c*e^(-kt) T = A + c*e^(-kt) T(0) = 90, so 30 + c = 90 c = 60 T(t) = 30 + 60e^(-kt) T(1) = 85, so 30 + 60e^-k = 85 e^-k = 55/60 -k = ln(55/60) k = 0.087 T(t) = 30 + 60e^(-.087t) we want when T=60: 30 + 60e^(-.087t) = 60 e^(-.087t) = 1/2 -.087t...
March 12, 2016

Calculus
dT/dt = -k(T-A) dT/(T-A) = -k dt ln(T-A) = -kt T-A = e^(-kt) T = A + e^(-kt) Now just plug in your numbers to find k and then solve for when T=60
March 12, 2016

Calculus
Nope. That condition y(-4) = e should have tipped you off that logs/exponentials were involved. dy/dx = 4y/x^2 dy/y = 4/x^2 lny = -4/x + c y = c*e^(-4x) note that the two c values are different. We could have said that lny = -4/x + lnc y = e^(-4/x + lnc) = e^(-4/x)*e^(lnc) = c...
March 12, 2016

Math
The number of odds and evens cannot differ by more than 1. 40 = 2/5, so 2 odds and 3 evens works 48 = 24/25 50 = 1/2 60 = 3/5 45 = 9/20 which cannot be. If there are 9 odds, there cannot be 11 evens.
March 12, 2016

Calculus
you need to find F(x) such that dF/dx = x^3-6x Using the power rule, that is just F(x) = 1/4 x^4 - 3x^2 + c Now, the definite integral is just F(3)-F(0) = (1/4 * 81 - 3*9 + c) - (0-0+c) = 81/4 - 27 = -27/4 Read your text on the meaning of the integral. Consider that it is a ...
March 11, 2016

Math
by small, do you mean in absolute value? If so, then since 2*5-10 = 0, 5 and 0 will have a product of zero. Otherwise, x(2x-10) has a minimum value of -12.5 when x = 2.5
March 11, 2016

Business math
solve for t in (1+.06/2)^(2t) = 3000/2000 (1.03)^(2t) = 1.5 2t log1.03 = log1.5 t = log1.5/(2log1.03) = 6.86 So, it will take 13.72 half-years
March 11, 2016

Algebra
y = 16/10 x
March 11, 2016

Math
circles, of course.
March 11, 2016

Math
or, better, 20..Andrew..9..Daniel..10
March 11, 2016

Math
20 ahead of andrew 30 behind daniel Now we know that 30+1+x = 2x+1+20 10=x So, there were 41 runners, in order: 30...Daniel...10 20...Andrew...20
March 11, 2016

Mathematics
Uing f for weight (force), we have f = kwh^2/l So, fl/(wh^2) is constant You need f such that 6f/(7*4^2) = (3*18)/(4*3^2) f = 28 tons
March 11, 2016

math
it's much easier if you just write 6-6x <= 4-5x 2 <= x
March 11, 2016

Math
c = kwt so, c/(wt) = k, a constant You want w such that 180/(3w) = 204/(340*4) 60/w = 3/20 w = 400
March 11, 2016

Algebra
which two factors of 24 add up to 10? which two factors of 45 differ by 4?
March 11, 2016

math/geometry PLEASE HELP ME!
Hmmm! The complement is indeed 40, but the supplement is 130. Don't see that choice. I suspect a typo.
March 11, 2016

math
well, each probability is 1/4, right?
March 11, 2016

2nd grade math
well, 7+5 = 12 what do you have to add to 8 to get to 12?
March 11, 2016

Geometry(so lost)
If the triangles are congruent, the corresponding angles are equal. So, m∠B = m∠Q 3v+4 = 8v-6 v = 2 So, m∠B = m∠Q = 10°
March 11, 2016

Geometry
reflection: (x,y,z) -> (x,-y,z) Now just apply the shifts.
March 11, 2016

math
(3*4*4*4)/16 = ?
March 11, 2016

math
perimeter 24 = 2*length + 2*width so, ...
March 11, 2016

math
50000 * .106/2
March 11, 2016

MATH
Consider triangles AEY and CEB. AE=CE (BE bisects AC) EY=EB (median is extended its own length) angles AEY and CEB are congruent (vertical angles) So, the two triangles are congruent (SAS). That means that AY=BC and is parallel. Now do the same with triangles ADX and BDC. The ...
March 11, 2016

Math
900(.11+.19)
March 10, 2016

Math
4(28+x) = 157+x
March 10, 2016

Algebra 2
I see you aren't going to make any effort, but just repost till someone does it for you. 6000 * 1.1^t now solve for when 1.1^t = 2
March 10, 2016

Algebra 2
14 * 0.75^n
March 10, 2016

Math
It's 12% for the whole year. You only have 15 days.
March 10, 2016

Math
Is interest charged on the amount of the overdrafts as well as the $7.82 fees?
March 10, 2016

Math
15 days is 1/24th of a year. So, charge 1/24 of the annual rate.
March 10, 2016

calculus
the slope of your line is 3/4 So, the slope of the perpendicular line is -4/3 The line through (0,-5) with slope -4/3 is y+5 = -4/3 x The two lines intersect at (-3,-1) Or, if you want to exercise your calculus, the distance from (0,-5) to any point (x,y) is d^2 = x^2 + (y+5)^...
March 10, 2016

Algebra 2
as with all exponentials, the domain is (-∞,∞) You know the range of a^x is (0,∞), so adjust that for the shifted function above.
March 10, 2016

math / geometry
go to jail - do not pass Go, do not collect an A grade.
March 10, 2016

6TH GRADE MATH
m = s/60
March 10, 2016

Math
I think you can get what you need here: http://stackoverflow.com/questions/3306838/algorithm-for-reflecting-a-point-across-a-line
March 10, 2016

math
it lands when the height is zero. That is when t ≈ 0.25 How did symmetry lead you to the answer of 0.2?
March 10, 2016

Trig
what do you mean the domain is the time per revolution? Surely the position is a function of time, not period.
March 10, 2016

Math
almost. watch the +/- signs
March 10, 2016

Geometry
good work so far. Now just solve the equations. Plug in the expressions for A and B, and you can then solve for C. Then work back to evaluate A and B, using the value of C.
March 10, 2016

Algebra
assuming the usual sloppiness with parentheses, you are correct.
March 10, 2016

Precalculus
f(x) = x^6 g(x) = 3-7x
March 10, 2016

Solid mensuration
not clear which part of the sphere is sitting on the table.
March 10, 2016

math 1149
not much information about A and D, is there?
March 10, 2016

math
T(3r-y)/(y^3+√r)=4 3Tr - Ty = 4y^3 + 4√r 3Tr - 4√r - (4y^3 + Ty) = 0 This is just a quadratic in √r, so you can use the quadratic formula: √r = [4±√(16+12y(4y^2+T))]/(6T) Not sure just where you want to take this.
March 10, 2016

math
2t^3 - t - 54 = 0 cubics are hard to solve algebraically. You will need a graphical or numeric method. See http://www.wolframalpha.com/input/?i=2t^3+-+t+-+54
March 10, 2016

math
I assume you want the area of each slice. That is just 1/8 the area of the whole pi, which is π/8 * (10 1/4)^2 ≈ 41.26
March 10, 2016

geometry
using similar triangles, s/6 = (s+15)/20
March 10, 2016

math
The function is poorly defined. t=3 or 4 fits into two different parts. (c) clearly 2 is the lowest cost (e) c(3) is defined in two ways. Fix your domain intervals. They cannot all be closed on both ends.
March 10, 2016

math
(a) x=5 is not defined. One of your intervals should include it. (b) clearly c=5 is the cheapest value. (c) similarly, c=15 is the most expensive c(10-c(3) = 15-5 = 10 You should graph the different pieces of the function to get an idea. If you cannot graph lines, you have ...
March 10, 2016

Math
the two pieces of data are redundant, since the area is always 1/2 the product of the diagonals. There is not enough info here to pin down the lengths. All we have is pq=72. Also, area and the product are ft^2, not ft.
March 10, 2016

math
y = k√x That is, y/√x = k, a constant. So, you want y such that y/√2401 = 47/√49
March 10, 2016

algebra
you keep asking the same question. I have discussed it several times. What is still bothering you? Have you tried google?
March 10, 2016

maths
bisect the chords. Now you have two right triangles, each with the same hypotenuse, r Since x^2+y^2 = r^2, if x is smaller (closer to the center) then y must be larger (the chord is longer)
March 10, 2016

Math
If you check, you will find that this is a right triangle. So, either of the legs can be considered the height.
March 10, 2016

Math
they have a common ratio, so (x-6)/(x+9) = 4/(x-6) You will find two values of x which work.
March 10, 2016

Calculus
dy/dx = 4y/x^2 dy/y = 4/x^2 dx lny = -4/x + c y = c e^(-4/x) Now use the condition to find c
March 10, 2016

Calculus
there are various Riemann sum calculators online. Or heck, drag out your calculator and do the math. Where do you get stuck? All those posts looks like a homework dump to me.
March 10, 2016

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