Thursday

October 27, 2016
Total # Posts: 45,391

**Quick Math Help**

these are all just arithmetic sequences. An = a + (n-1)d Sn = n/2 (2a + (n-1)d) see what this gives you

*October 11, 2016*

**mathe**

16/2 (2a+15d) = 240 4/2 (2(a+16d) + 3d) = 220

*October 11, 2016*

**Algebra**

(300/132)*5 - 3

*October 11, 2016*

**Maths**

the amounts are 2x and 5x 7x = 490 so, ...

*October 11, 2016*

**Calculus**

ds/dt = -2/27 t + 2/√t = (54-2t^(3/2))/(27√t) ds/dt=0 when 54 - 2t^(3/2) = 0 t^(3/2) = 27 t = 9 now just find s(9)

*October 11, 2016*

**Maths**

3/4 = 24/32

*October 11, 2016*

**Pre- Algebra**

C and D are correct (almost) any number with an exponent between -7 and 7 will work. I suspect a typo somewhere.

*October 11, 2016*

**maths**

draw a diagram. If the building has height h, and the chopper is x above the building h cot60° = (h+x)cot30° Both of these are equal to the distance of P from the building. Once you have that, you can find h and x. Without knowing that or h, you cannot find x.

*October 11, 2016*

**Calc**

sketch the region. It will be clear that ∫[0,8] ∫[∛y,2] 8e^x^4 dx dy = ∫[0,2] ∫[0,x^3] 8e^x^4 dy dx = ∫[0,2] 8x^3 e^x^4 dx = 2e^x^4 [0,2] = 2(e^16-1) Nice trick, since e^x^4 does not integrate well.

*October 11, 2016*

**Calc**

∫[0,1]∫[√x,1] 8(y^3+1) dy dx = ∫[0,1]8(y^4/4+y)|[√x,1] dx = ∫[0,1]8[(1/4+1)-(x^2/4+√x)] dx = ∫[0,1] -2x^2 - 8√x + 10 dx = (-2/3 x^3 - 16/3x^(3/2) + 10x [0,1] = -2/3 - 16/3 + 10 = 4

*October 11, 2016*

**Calc**

Not sure just what you intended. I (sort of) see ∫[4,12]∫[0,3y] 5e^(x^2) dx dy It seems wrong; maybe you could fix it so it is (a) correct (b) readable

*October 11, 2016*

**Pre Cal**

Using the law of cosines, the distance z is z^2 = (2.5*340)^2 + (2*340)^2 - 2(2.5*340)(2*340)cos(141°) z = 1443 bearing: 90-θ where tanθ = (2*340*cos51°)/(2.5*340+2*340*sin51°) θ = E 17.25° N or 72.75°

*October 11, 2016*

**math**

Let t be the number of years since 1991. Then we have P(t) = 114 * (120/114)^(t/(1997-1991) = 114 * 1.05263^(t/6) Now find P(2014-1991) = P(23)

*October 11, 2016*

**Math**

ok - fix it and go from there.

*October 11, 2016*

**Math**

start with: b/g = 3/5 g = b+20

*October 11, 2016*

**math**

well, what is their greatest common factor? Hint 7 does not divide either 27 or 36. and why did you write each answer twice?

*October 11, 2016*

**Calculus**

do this like the other. Find the xy-plane boundary of the base, and set the height to z = 3x+3y

*October 11, 2016*

**Calculus**

The hypotenuse of the base is the line y = (7-x)/3 So, add up all the small solids with base dx dy and height z v = ∫[1,4]∫[1,(7-x)/3] 7xy dy dx

*October 11, 2016*

**Math - correction**

Not quite. b/g = 3/7 g = b+20 b = g-20 = 7b/3 - 20 4b/3 = 20 b = 15 check: 15/35 = 3/7

*October 11, 2016*

**math**

type it into google - it will calculate for you or (just a thought), use your own calculator! If you want the answer as a fraction, type it in at wolframalpha.com

*October 11, 2016*

**physical science**

velocity is m/s. So, 20m/2.3s = 8.7 m/s

*October 11, 2016*

**physics**

so many unanswered questions. Does the ball roll around inside? Bounce off the ends? Shaken up/down or side-side? Surely there is some further context.

*October 11, 2016*

**science**

R = p * L/A You have the p and A, but the resistance R depends on the length.

*October 11, 2016*

**Math**

not sure what quotientshapes are, but yes, you can get a reasonable approximation by doing 6/31 6/31 = 0.195 5.8/30.8 = 0.188

*October 11, 2016*

**Math**

by 1.30^2 = 1.69 or 69%

*October 11, 2016*

**Math**

a 4x4 square

*October 11, 2016*

**Math (Limits)**

f(x) = 2x^2 − 8x f(x+Δx) = 2(x+Δx)^2 − 8(x+Δx) now just crank it out, as in the examples from your text.

*October 11, 2016*

**math**

the circumference of a circle of radius 4.2

*October 10, 2016*

**Math**

right if c^2 = a^2+b^2

*October 10, 2016*

**MATH**

solving rational equations solve check your answer 5/3x+1=2

*October 10, 2016*

**physics**

Since the force is inversely proportional to the square of the distance, it will be g * (R/(R+8600))^2 where R is the earth's radius.

*October 10, 2016*

**Math**

hard to mix commas with operators

*October 10, 2016*

**Math**

5/3xt1=2

*October 10, 2016*

**math**

tanA = 26.0/65.2 B = 90-A

*October 10, 2016*

**math**

x/67 = 71/100

*October 10, 2016*

**Math**

since time = distance/speed, if the boat's speed was s, then 70/(s-5) = 95/(s+5) s = 33 avg speed = totaldistance/totaltime = (70+95)/(70/28 + 90/38) = 1254/37 or 33.89 mi/hr

*October 10, 2016*

**Maths**

"sum" means "add" I assume your calculator can do that...

*October 10, 2016*

**Math help**

x = tanθ x^2+1 = sec^2θ dx = sec^2θ dθ and now your integrand becomes tan^3θ/secθ * sec^2θ dθ = tan^3θ secθ dθ = tan^2θ (secθ tanθ dθ) = (sec^2θ - 1) (secθ tanθ dθ) let u = secθ...

*October 10, 2016*

**physics**

Viy = 11 sin75° h = Viy t - 4.9t^2 solve for t in h=0, then Vy = Viy - 9.8t Use the t from above to get Vfy

*October 10, 2016*

**Quantitative Reasoning**

depends on the amount of ice, doncha think? Also, you need to know the surface area of the oceans. A large ocean will rise less than a small one for the same amount of ice. Also, a given volume of ice produces less volume when melted. There is so much missing in this question.

*October 10, 2016*

**Algebra**

x = number of $1 reductions price: 50-x demand: 600+20x R(x) = (50-x)(600+20x)

*October 10, 2016*

**Pre-Calculus**

check out the volume of a spherical cap: https://en.wikipedia.org/wiki/Spherical_cap

*October 10, 2016*

**maths**

get out your calculator or, just type that into the google search box -- it will calculate for you.

*October 10, 2016*

**pre-calc**

(ax^2 + bx + c)(x+2) + d = ax^3 + (2a+b)x^2 + (2b+c)x + (2c+d) so, a=3 2a+b = 0 2b+c = 2 2c+d = 1 now just crank it out.

*October 10, 2016*

**Maths**

429.07 * 100 = 42907

*October 10, 2016*

**college algebra**

You may want the height (h) or the length (L). h/20 = 0.3 L^2 = 20^2 + h^2

*October 10, 2016*

**Math**

Or, you can say that if |x| = 4 x = ±4 so, if |x-8|-15 = -6 |x-8| = 9 x-8 = ±9 ...

*October 10, 2016*

**Math**

Let's say there are m marbles. The clues given are: b+r+y = m r/m = 2/5 b/y = 5/7 r = 2m/5 y = 7b/5 so b+r+y = m b+(2m/5)+(7b/5) = m 12b/5 = 3m/5 b/m = (3/5)(5/12) = 1/4

*October 10, 2016*

**college algebra**

If the statue's height is h, then using similar triangles (from the diagram you drew, right?): h/c = a/b Now just plug in your numbers and solve for h

*October 10, 2016*

**Math**

If you followed those instructions, even without the typos, I'm sure you were confused! 3x + 9 = 7x - 11 subtract 3x: 9 = 4x-11 add 11: 20 = 4x divide by 4: 5 = x

*October 10, 2016*

**Math**

yes, 3 is one answer

*October 10, 2016*

**Math**

number between 600,000 and 700,000 6xx,xxx The digit in the hundreds place is 3. 6xx,3xx The digit in the ten thousands place is 1 more than the digits in the thousands and hundreds place. 643,3xx The sum of the digits in the ones and tens place equals the digits in the ...

*October 10, 2016*

**science**

1/R = 1/40 + 1/60

*October 10, 2016*

**Physics**

PV=kT since P is constant, V/T = k/P is constant. Thus, you want V such that V/273 = 50/293

*October 10, 2016*

**Physics**

think about it. the dropped coin reaches you with exactly the same velocity as you threw the sandwich.

*October 10, 2016*

**math**

9-7 = 9+(-7)

*October 10, 2016*

**math**

(10 2/3) / (3/4) = 32/3 * 4/3 = 128/9 = 14 2/9 So, there will be 14 plants fertilized, with some left over.

*October 10, 2016*

**physics (question impossible to solve)**

huh - I guess it's impossible to solve. Or, maybe you just need to review what static friction is.

*October 10, 2016*

**Physics**

v = vo + at now just plug in your numbers. The speed changes by 1.24 m/s every second.

*October 10, 2016*

**physics**

The triple product is just the determinant |ax ay az| |bx by bz| |cx cy cz|

*October 10, 2016*

**Calculus**

you want the tangent line to the curve at x=0. In a small neighborhood, the curve will stay close to the tangent line. (In fact, any curve is "straight" in a small enough interval!) So, you know that at x=0.3, the curve will be fairly close to the tangent line, which...

*October 10, 2016*

**mathematics**

LCM(24,30,36) = 360

*October 10, 2016*

**Geometric progression**

ar^4 = 81 ar = 24 r^3 = 81/24 = 27/8 r = 3/2 Now find a.

*October 10, 2016*

**Algebra**

separate it into 2+5+8+... and 3+6+9+... add the two sequences together. Each is easy to figure, right? Or, make it a single sequence 6n-1 ... 5+11+17+...

*October 10, 2016*

**calculus**

√(4x+y)+√(3xy) is not a curve. It is a surface. I guess you meant √(4x+y)+√(3xy) = 10 Hmmm. Maybe not, since that does not lead to the value you give. Try again with the post, and maybe show some intermediate steps.

*October 10, 2016*

**Math**

ar^7 = 348 ar^4 = 48 divide: r^3 = 29/4 now you can find a.

*October 10, 2016*

**Calculus**

dy/dt = cosz dx/dt = -2sinz dy/dx = -1/2 cotz d^2y/dx^2 = [d/dt(dy/dx)]/(dx/dt) = -1/2 csc^2(z) / -2sinz = -1/4 csc^3(z) too bad you didn't show any of your work...

*October 10, 2016*

**calculus**

sin(xy)+x^5+y^5=c cos(xy)(y+xy') + 5x^4 + 5y^4 y' = 0 y*cos(xy) + x*cos(xy)y' + 5x^4 + 5y^4 y' = 0 (x*cos(xy) + 5y^4)y' = -(y*cos(xy) + 5x^4) y' = y*cos(xy) + 5x^4 - ------------------------- x*cos(xy) + 5y^4

*October 10, 2016*

**Math**

x^2-3x+2 = (x-1)(x-2)

*October 10, 2016*

**Calculus**

depends. Is the region a 2x2 grid, or a 1x4 grid? In the first case, it will be 600x600. In the 2nd case, it will be 900x360.

*October 10, 2016*

**MATH**

no way to tell

*October 10, 2016*

**maths**

Figure the price per lemon divide the selling price by the cost (15/8) / (10/6) = 9/8 = 1.125 or a 12.5% profit

*October 10, 2016*

**MATH**

fix the typo

*October 10, 2016*

**Algebra**

they made 54 candles in 2 hours. Use that rate.

*October 10, 2016*

**Maths**

here's what I get, as you have written it. http://www.wolframalpha.com/input/?i=2%C3%B7%E2%88%9A5%2B%E2%88%9A3%2B1%C3%B7%E2%88%9A3%2B2-3%C3%B7%E2%88%9A5%2B%E2%88%9A2 I suggest some parentheses if you had intended other groupings

*October 9, 2016*

**Math**

just divide by the earth weight.

*October 9, 2016*

**physics**

If A has 10 times the mass, Fa/Fb = 10 If A is 10 times as far, Fa/Fb = 1/100 Now combine the two.

*October 9, 2016*

**math**

1/x - 1/(x-2) = -2/15

*October 9, 2016*

**math**

The reciprocal of a number minus the reciprocal of two less than the number is -2/15. find the number.

*October 9, 2016*

**Maths**

8 times as much as he saves.

*October 9, 2016*

**pre cal**

the fraction remaining after t hours is .64^(t/9) now plug in your numbers

*October 9, 2016*

**Math**

.50x + .20(45-x) = .30(45)

*October 9, 2016*

**math**

x+y=40 3.6x+4.6y = 156 now crank it out.

*October 9, 2016*

**precalculus**

oops - forget the sin example. Booooguss! I was thinking arcsin. 1/sin(4π11)

*October 9, 2016*

**precalculus**

sin(1/4π11) whatever that means or sec(π/2-4π11) co- means complementary angle.

*October 9, 2016*

**Math**

Set the partial derivatives to zero for extrema. Both must be zero.

*October 9, 2016*

**Math**

since distance = time * speed, 3(x + x-4) = 400-40

*October 9, 2016*

**precalculus**

see related questions below again

*October 9, 2016*

**Math**

(3/4 - 1/5) pi

*October 9, 2016*

**Math**

21 49/10 ...

*October 9, 2016*

**math**

the "direction change" rule is just a shortcut for when things move from one side of the inequality to the other. When adding and subtracting, or multiplying/dividing by a positive value, the direction never changes. -4x < 8 divide by -4 and change direction: x &...

*October 9, 2016*

**value**

max height reached at 2 seconds. use that.

*October 9, 2016*

**MATH**

7.50 * 3

*October 9, 2016*

**Variation**

D = kT^2 when T=13, D = 169k when D=648, T = √(648/k) Supply the missing info, and you can get numbers.

*October 9, 2016*

**maths(cbse)**

Draw a diagram. The half-chords are legs of right triangles, with the radius as hypotenuse. The two triangles require that r^2 = 4^2 + 3.5^2 r^2 = 8^2 + 5^2 Clearly the two values do not agree, so the assertion is false.

*October 9, 2016*

**Calculus, Related Rates**

Why are you looking for speeds? The question is about distance. Let's assume that the miles are nautical miles, so no conversions are necessary. At time t hours, the distance z is found using z^2 = (60-15t)^2 + (36-10t)^2 = 325t^2 - 2520t + 4896 2z dz/dt = 650t - 2520 The ...

*October 9, 2016*

**MATH**

If John ate half of what Peter ate, clearly Peter ate more. so, what is 1/2 of 2/8? what is 1/2 of 2?

*October 9, 2016*

**math**

see related questions below. always a good idea before posting the same problem again!

*October 9, 2016*

**Algebra 1**

13+ w/7 = -18 subtract 13: w/7 = -31 multiply by 7: w = -217

*October 9, 2016*