Friday

May 27, 2016
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*

**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*

**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*