Friday
May 27, 2016

Posts by steve

Total # Posts: 40,859

Math
Reiny did this already at http://www.jiskha.com/display.cgi?id=1461201861
April 21, 2016

Math
organize things a bit better y = 3x^2+4x-8 y = 2x^2+4x-3 so, 3x^2+4x-8 = 2x^2+4x-3 x^2-5 = 0 x = ±√5 now use that to find y.
April 21, 2016

Dosage calculations
since the rate is 125ml/hr, why does it say 150 ml/hr? Anyway, your calculations look good. but watch the units. 1000ml/8hr = 125 ml/hr, not 125ml 125ml/hr * 3hr = 375ml
April 20, 2016

Math
6C4 .4^4 .6^2 = 0.138
April 20, 2016

math
after t years, p(t) = 23000 * 1.025^(t/8) so, p(25) = 24845 p(-10) = 22301
April 20, 2016

Math
dp/dt = -.06p dp/p = -.06 dt lnp = -.06t p = c e^(-.06t) where c is the starting value.
April 20, 2016

Math
your complex number is garbled.
April 20, 2016

Math
sine the rate of decrease is 14% of the amount present, dp/dt = -.14p dp/p = -.14 dt lnp = -.14t + c p = c e^-.14t here, c is the original amount when is only .22 left? e^-.14t = .22 -.14t = ln.22 t = ln.22/-.14 = 10.8 years
April 20, 2016

Geometry
well, I don't have a diagram, but if the pentagonal shape is just a rectangle with a triangle on top, its area is 8.5 * 17 + 1/2 * 17 * √(12^2-8.5^2) = 216.5 in^2 The round pizza has an area of 49π = 153.9 in^2 So, the cost of the home-plate pizza should be $10....
April 20, 2016

Math
Not sure what that description means, but if it is a cylinder atop a cone of radius 5 and height 4, then its volume is π/3 * 5^2 * 4 + π * 5^2 * 2 = 250π/3 So, the bottom cone must have the same volume: π/3 * 6^2 h = 250π/3 36h = 250 h = 250/36 = 6.9 cm
April 20, 2016

math log rules / chemistry
picking up where you left off, and fixing the minus sign you lost, (E2-E1)/0.05916 = -log[F+S] + log[F] (E2-E1)/0.05916 = log(F/[F+S]) 10^[(E2-E1)/0.05916] = F/(F+S) 10^[(E2-E1)/0.05916]F + 10^[(E2-E1)/0.05916]S = F F = 10^[(E2-E1)/0.05916]S ------------------------------ (1-...
April 20, 2016

help azap
length is ft area is length*width = ft*ft = ft^2 volume is length*width*height = ft*ft*ft = ft^3
April 20, 2016

Statistics
play around with Z table stuff here: http://davidmlane.com/hyperstat/z_table.html
April 20, 2016

math
no solutions. |x+1| is never negative, so adding 6 can never give a sum of 3. trick question.
April 20, 2016

math
180/x = tan 27°
April 20, 2016

Maths
review the basic trig functions. You will see that if the height is h, h cot13.5° - h cot 14.8° = 100
April 20, 2016

Further maths
just use what you know about AP's and GP's: (a+2d)/a = (a+8d)/(a+2d) a+6d = 14 AP: 2,4,6,8,... GP: 2,6,18,... Now you can easily find terms and sums.
April 20, 2016

mathematics-abstract equations
You know they are all perfect squares 64,81,9
April 20, 2016

Math
The trend will be positive, but depending on the age range, it may or may not look linear.
April 20, 2016

Math
assuming you meant a 10-ft ladder, then the height is √(10^2-2^2) = √96 If not 10, then fix it and use the same formula.
April 20, 2016

Math
0.42
April 20, 2016

Analytic Geometry
the major axis is vertical, so we have center: (0,0) a=13, b=12 c^2 = a^2-b^2, so c=5 vertices: (0,±13) covertices: (±12,0) foci: (0,±5) eccentricity e = c/a = 5/13 length of latus rectum is 2b^2/a = 2*144/13, so the latera recti are the lines through the ...
April 20, 2016

math
that's rubbish. Just typing in ellipse, I got many hits, and as usual, wikipedia had a very good article. https://en.wikipedia.org/wiki/Ellipse
April 20, 2016

math
depends on the conic section. google is your friend. Just look up "parabola" or "ellipse" etc for many discussions of their properties.
April 20, 2016

Calculus
-170 = -32t now, s = 16t^2
April 20, 2016

Analytic Geometry
well, you have a=5,b=3, so c=4. Now you can use that to proceed.
April 20, 2016

math
well, the difference d = (50-29)/(16-9) = 3 T20 = T16 + 4d ...
April 20, 2016

math
clearly, 2 3/4 + 3 1/3 miles
April 20, 2016

Math
since 1 cup is 3 times as much as 1/3 cup, she will need 3 times 4/5 c of flour.
April 20, 2016

math
3/4 * x = 2/5 (380-x) + 32 x = 160 Kelvin gets 160, spends 120 Winnie gets 220, spends 88
April 20, 2016

Maths
12000L / (150L/min) = 80 min
April 20, 2016

Maths
yes. That is the way they are defined.
April 20, 2016

math
42
April 20, 2016

Calculus (easy)
(2√2,5π/4)
April 20, 2016

Calculus
(i) v = ∫[0,1] π(R^2-r^2) dy where R^2=2-y^2 and r=y^2 (ii) v = ∫[0,1] 2πrh dy where r=y and h=√(2-y^2)-y^2
April 20, 2016

science
To conserve water, an animal's kidneys can pump ions across cell membranes, allowing water to move by
April 19, 2016

Trigonometry
well, since tan60° = √3, 2θ-34 = 60
April 19, 2016

trig
to find A, sinA/63 = sin53°/50 having C and A, B is easy since A+B+C=180. get b using law of sines or law of cosines.
April 19, 2016

Polar, Cylindrical, and Spherical Coordinates
good. I thought it would make sense if you looked at it a while.
April 19, 2016

Polar, Cylindrical, and Spherical Coordinates
no help from my earlier comments? http://www.jiskha.com/display.cgi?id=1461018078
April 19, 2016

math
15 km
April 19, 2016

Math
20/(3 1/2) = 20/(7/2) = 20*2/7 = 40/7 = 5 5/7 so, 5 pieces, plus 5/7 of a piece left over. Since one piece is 7/2 feet, 5/7 * 7/2 = 5/2 = 2 1/2 feet left over. Or, 20 - 5(3 1/2) = 20 - 17 1/2 = 2 1/2 ft left over
April 19, 2016

Math
if there are x liters of 25% juice, then there are (20-x) of 55% juice. So, .25x + .55(20-x) = .21(20)
April 19, 2016

geometry
with θ in radians, rθ = 8/5 since c=12, r = 12/(2π) = 6/π θ = (8/5)(π/6) = 4π/15 = 48°
April 19, 2016

Algebra. NEED HELP ASAP PLEASE
what is x when y=0? the intercept indicates how long it will take for sales of such cell phones to stop.
April 19, 2016

math
2^16 = 65536
April 19, 2016

Calculus
clearly e^(-6/√n) -> e^(-6/∞) = e^0 = 1
April 19, 2016

Pre-Calc
clearly -1 is not a solution, since log(-1) is not real. log3(x(x-2)) = 1 x^2-2x = 3 x^2-2x-3 = 0 (x-3)(x+1) = 0 so, yes, x=3 is a solution, but -1 is extraneous.
April 19, 2016

math
At distance x, the shadow has length s, so s/6 = (s+x)/8 s/6 = s/8 + x/8 4s = 3s+3x s = 3x ds/dt = 3 dx/dt so, the length of the shadow shrinks at a constant rate of 9 ft/s.
April 19, 2016

geomtry
have to know the linear scale. Areas scale by that value squared.
April 19, 2016

math
clearly, also 97 all the other prime factors must be less than 97, since they are factors of numbers from 1 to 96.
April 19, 2016

math
20 x^2 y But I suspect a typo.
April 19, 2016

Geometry
since AB=AC, ABC is isosceles, and AN, besides being an altitude, is another median, like CM. The medians intersect 2/3 of the way from each vertex to the opposite side. The altitude AN forms two 5-12-13 right triangles, so AN=12, and AX=8.
April 19, 2016

Algebra
Since there are two = signs, I'll assume the second one is a +. Then we have 7 – 5(2 – x) = –(x – 8) + 11/6 7 - 10 + 5x = -x + 8 + 11/6 5x+x = 8 + 11/6 - 7 + 10 6x = 77/6 x = 77/36 I expect there's a typo I misread, so just fix it and then follow ...
April 19, 2016

math
w(5w-23) = 42 Now solve for w. Or, consider that two factors of 42 are 6 and 7.
April 19, 2016

Math
since the angles add to 180°, angle F is 72°. Using the law of sines, DF/sin72° = 24/sin45° x = 32.28 So, did you just guess at A?
April 19, 2016

Math
-4+12 /(-3) 10+3(-2) -4 -4 10 - 6 I suspect another symbol is missing: ...(-3) ? 10 ... Maybe also after the +12 If so, fill it in and continue.
April 19, 2016

Math
or, once you have A and C, B = 180-(A+C)
April 19, 2016

Math
tan(θ)/ sec(θ) − cos(θ) = tanθ * cosθ - cosθ = sinθ/cosθ * cosθ - cosθ = sinθ - cosθ
April 19, 2016

math algebra
1.05x = 18165
April 19, 2016

Math
57 = 3s
April 19, 2016

Algebra
no, 45 = 9*5 9! = 9*8*7*6*5*4*3*2*1 = 362880 How ever did you decide on A?
April 19, 2016

Math
rubbish There's a 25% chance of not growing. So, P(3 not) = 7C3 .25^3 .75^4 = 0.17
April 19, 2016

Further maths
a = 3d d = 8 so, a=24 and the AP is 24,32,40,...
April 19, 2016

Physics
recall that F = k(q1 q2)/d^2 now just plug and chug, after looking up k.
April 19, 2016

Math
d = 40074/pi
April 19, 2016

Math
I don't see a question, but the expected value E = 3(3/34) + 2(10/34) - 1(21/34) = 4/17 = $0.24
April 19, 2016

math
C
April 19, 2016

Calculus
there are many handy Riemann um calculators online, such as http://www.emathhelp.net/calculators/calculus-2/riemann-sum-calculator/
April 19, 2016

Calculus (Urgent, please)
The curves intersect at (±1.25,1.56) using symmetry, the area is a = 2∫[0,1.25] √(4-x^2) - x^2 dx = 3.35
April 19, 2016

Math
7/10 + 7/20 = 21/20 So, 1/20 prefer both. But how can someone prefer two days?
April 19, 2016

math
your files are not available to us online.
April 19, 2016

math
9999 * 100
April 19, 2016

Math
y = x+12 3y-5x = 20
April 19, 2016

Math No!
nope. He spent that money, and 700 was left. So, x - x/4 - 2x/5 = 700 x = 2000 1/4 of 2000 = 500 2/5 of 2000 = 800 So, he spent 1300, leaving 700
April 19, 2016

Math
since there is no question, I see little point in hinting at answers.
April 19, 2016

science
try google
April 19, 2016

maths
not sure what "to s" means, but a suitable trapezoid has only two right angles.
April 19, 2016

math
last I checked, there were 435 reps. and that's there, not their!
April 19, 2016

Maths
√(12+6√3) + √(12-6√3) 12+6√3 = 9 + 6√3 + 3 = (3+√3)^2 so, you have just 3+√3 + 3-√3 = 6
April 19, 2016

advanced calculus
The central arm's endpoints are a circle of radius 100: x = 100cosθ y = 100sinθ At θ=0, the arm is horizontal. So, assuming the wheel's boarding position is also at θ=0, and its angle is relative to the central arm, the boarding location's ...
April 19, 2016

Calculus
The region is just a square of side √2, with its center at (2,1). Using the Theorem of Pappus, the surface area is thus the perimeter of the square times the distance traveled by its centroid: a = 4√2 * 2π = 8π√2 Doing it using the usual definition...
April 19, 2016

math
you really need to work on your text formatting.
April 19, 2016

Calculus I
you can verify this at http://www.wolframalpha.com/input/?i=plot+y%3D1%2F12+x^3,+y%3D4x-32%2F3,+0%3C%3Dx%3C%3D6
April 19, 2016

Calculus I
f(x) is a constant, so the slope is zero everywhere!!
April 19, 2016

Pre-Calc
logb(4) sqrt((x^7 y^2)/(z^4)) well, I'm not sure what logb(4) has to do with it, but log(a^n) = n*log(a) so, log(√(x^7y^2/z^4)) = 1/2 (7logx + 2logy - 4logz) = 7/2 logx + logy - 2logz regardless of the base.
April 18, 2016

Math college grade 12
well, 0.8^t = 1/300 t log0.8 = -log300 ...
April 18, 2016

Math-Trig
the diagonals bisect each other, and are perpendicular to each other. So, draw the figure, and note the four right triangles formed.
April 18, 2016

geomatry
(-1-(-5))/(-4-2) = 4/-6 = -2/3
April 18, 2016

math
you can't. If all you have is the volume, it could be a cube of side ∛10 or, a brick with sides 1 x 2 x 5 2 x 2 x 2.5 4 x 2 x 1.25 10 x 5 x 0.2 etc.
April 18, 2016

Calculus
(ds)^2 = (dx/dt)^2 + (dy/dt)^2 = (-sint + sint + tcost)^2 + (cost - cost + tsint)^2 = t^2cos^2(t) + t^2sin^2(t) = t^2 so, ds = dt that's pretty easy to integrate, right? Hmmm. I missed that ^2 hanging out there. Is y(t) = sint - t(cost)^2 or y(t) = sint - tcos(t^2)? In ...
April 18, 2016

Solid Mensuration
google is your friend. You might start here: http://www.contracosta.edu/legacycontent/math/stararea.htm
April 18, 2016

Math
5n+25q = 460 n+q = 28 now just solve for n and q.
April 18, 2016

Geometry
looks good to me.
April 18, 2016

Geometry
at the fold. unless you fold it the other way, and then it would still be the 50-yd line...
April 18, 2016

Math
If the dimensions are x and y, then if the change fraction was r, xy = 300 (xr)(yr) = 363 xyr^2 = 363 r^2 = 363/300 r = 1.1 so, a 10% increase was used.
April 18, 2016

math
c+t=30 3c = 2t
April 18, 2016

Math
h(t) = 1 + vt - 16t^2 max height is reached at t = v/32, so 1 + v(v/32) - 16(v/32)^2 = 35 v = 8√34 h(t) = 1 + 8√34 t - 16t^2 h=0 at t=2.94 v(t) = 8√34 - 32t, so when h=0, v = 8√34 - 32(2.94) = -47.43 ft/s
April 18, 2016

Trigonometry
well, geez, just solve the equation. r = v^2sin2θ/g 1/32 1200^2sin(2θ) = 3000 sin2θ = (32*3000)/1200^2 = 1/15 Of course, there are two solutions, since sinθ is positive in [0,pi]. But you want the minimum value.
April 18, 2016

Math
clearly the answer cannot be 1, since that would mean you always get tails or roll less than 4. there are 12 possible outcomes, easy to list them. 1/2 give tails 1/2 * 3/6 = 1/4 gives heads and n<4. 1/2 + 1/4 = 3/4 or, consider P(heads & n>=4) = 1/2 * 1/2 = 1/4 you want ...
April 18, 2016

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