# oobleck

Most popular questions and responses by oobleck
1. ## Geography

There's 300 miles of air pushing down from above, right?

posted on May 22, 2019
2. ## Math

1 hour that's what you said, right?

posted on May 22, 2019
3. ## Math

42

posted on May 22, 2019
4. ## Maths

dx/dy = (dx/dt)/(dy/dt) (cost - t sint)/(1+cost) d^x/dy^2 = d/dy (dx/dy) = d/dt (dx/dy) dt/dy = (d/dt (dx/dy))/(dy/dt) = -(sint(t sint+2) + t cos^2(t) + cost(t+sint))/(1+cost) at t = pi/2 that is -(pi/2 + 2)

posted on May 22, 2019
5. ## math

If the width is w, then we know that (12+2w)(9+2w) - 12*9 = 100 Now just find w.

posted on May 22, 2019
6. ## General Calculus

if that confuses you, just recall the quotient rule for derivatives, and implicit differentiation.

posted on May 21, 2019
7. ## General Calculus

you know that tanθ = y/x sec^2θ dθ/dt = (x dy/dt - y dx/dt)/x^2 so just plug in your numbers.

posted on May 21, 2019
8. ## algebra

or just leave it as 1/6 That is the exact answer. Using a decimal value will only give an approximation. Don't feel you always have to use decimal values, unless they are requested. Probabilities are often expressed as fraction.

posted on May 21, 2019
9. ## Math

if it depreciates by 5.1%, that means that each year its value is 94.9% what it was the year before. So, after 8 years, the value is 9250 * 0.949^8 = 6085.15

posted on May 21, 2019
10. ## math

Recall that if the angle x subtends two arcs A and B, with A > B, then x = 1/2 (A-B)

posted on May 21, 2019
11. ## Maths

just find h such that π/3 (15/2)^2 * 12 = π*(10/2)^2 h that is, 225π = 25π h

posted on May 21, 2019
12. ## Math

is every number greater than one? No. Think a little more on it.

posted on May 21, 2019
13. ## Matrice Equation

In that case, ya got me. Not sure how you would go about converting the matrix to a form involving just 1's and 0's. Maybe you could clarify a bit... What does the problem actually say? You need to use row manipulations (elimination) to get something on

posted on May 21, 2019
14. ## Matrice Equation

two matrices one matrix Not sure what you so with symbolabs, but to solve the equation AX = B you multiply on the left by A-1, giving X = A-1B See it written out at

posted on May 21, 2019
15. ## Math

you got the first one, but missed the other two. 12+4m = 24 4m = 12 m = 3 d-6 > -4 d > 2 Note that this one does not have a single answer. ANY number greater than 2 will make the sentence true. You solved the equation d-6 = 4

posted on May 21, 2019
16. ## Maths

well, 7x4 = 28 maybe you can take it from there.

posted on May 21, 2019
17. ## math

well, one ratio is clearly 31:7 there are others possible, depending on what it is you're comparing.

posted on May 21, 2019
18. ## maths

just use the definition of even/odd even: f(-x) = f(x) odd: f(-x) = -f(x) It may be neither, ...

posted on May 21, 2019
19. ## Math

54=9*6, so 7:9 = 7*6 : 9*6 = 42:54

posted on May 21, 2019
20. ## chemistry

so, what is the volume of a lead atom? what is the mass of a lead atom? How are they packed? Since the crystal lattice affects density on a large scale, maybe you just want the density of a single atom. In any case, density = mass/volume

posted on May 21, 2019
21. ## Math

sorry, @Arya better try again

posted on May 21, 2019
22. ## physics

an LED on your computer a 50,000 ton diesel locomotive

posted on May 21, 2019
23. ## Math

x + 8 = -20 right - check your work >wink wink< hmmm. I don't see any ...

posted on May 21, 2019
24. ## Maths

complete the squares and it becomes clear: 36x^2+36y^2-24x-36y-23=0 36x^2-24x + 36y^2-36y = 23 36(x^2 - 2/3 x) + 36(y^2-y) = 23 36(x^2 - 2/3 x + 1/9) = 36(y^2 - y + 1/4) = 23 + 36(1/9) + 36(1/4) 36(x - 1/3)^2 + 36(y - 1/2)^2 = 36 (x - 1/3)^2 + (y - 1/2)^2

posted on May 20, 2019
25. ## Math

that was mean? I merely suggested what might lead you to the correct answer, since your choice was wrong.

posted on May 20, 2019
26. ## Maths

Just add up all the weights if there are g girls, then you know that 55*8 + 48g = 50.8(8+g) Now just solve for g

posted on May 20, 2019
27. ## Math

I think you need to review what an integer is. and what those three dots ... mean

posted on May 20, 2019
28. ## Science

all look good.

posted on May 20, 2019
29. ## Math

well, all absolute values are positive all positives numbers are greater than any negative number. With that, you can pick the right choice(s). As written, there are two. So, if you only get one choice, there's a typo somewhere.

posted on May 20, 2019
30. ## Chemistry

posted on May 20, 2019
31. ## Chemistry

the balanced equation is 4Al + 3O2 = 2Al2O3 so, how many moles of Al do you have? You get half that many moles of Al2O3 now convert back to grams

posted on May 20, 2019
32. ## chemistry

assuming you retain constant temperature, PV=kT remains constant. So, you just need to find P such that P*5 = 1*7.5

posted on May 20, 2019
33. ## Math

that would be 500(1 + 0.045*3) = _________

posted on May 20, 2019
34. ## Physics

1A = 1C/s so, how many electrons in 600 seconds? How many electrons per molecule deposited? Now you can figure the # molecules, and thus the # moles, and thus the mass

posted on May 20, 2019
35. ## Math

formula for area of parallelogram is, of course, area = base * height

posted on May 20, 2019
36. ## Physics

Let A's initial velocity be in the + direction (to the right) If the two initial velocities are Va and Vb, then to conserve momentum we need .25Va + .35*0 = .25(-0.12) + .35(0.65) solve for Va Now you can figure the total KE (1/2 mv^2) before and after

posted on May 20, 2019
37. ## physics

that would be 5(1,0,-1)+2(1,2,1)+3(1,-1,-3) = (10,1,-12)

posted on May 20, 2019
38. ## Chemistry

how many moles HCl available? how many moles KOH was used? each mole of KOH neutralized 1 mole of HCl Now, knowing how many moles of HCl are left, it will take that many moles of NaOH, so convert that to ml of .02M NaOH.

posted on May 19, 2019
39. ## Maths

area = 2pi*r(r+h) so, plug in your numbers and solve for h

posted on May 19, 2019
40. ## math

for every 2 girls, there are 3 boys to choose from 2/5 of 20 is 8

posted on May 19, 2019
41. ## Calculus

Yeah, I thought of that, and you're probably right. You should talk to your teacher and ask what they meant by "critical" values. When we're talking calculus, that has a certain special meaning, not just "values of f'(x)"

posted on May 19, 2019
42. ## Physics

volume = area * thickness now just plug in your numbers

posted on May 19, 2019
43. ## math

surely that would be 1/6

posted on May 19, 2019
44. ## Calculus

#2 ok #3 my bad - you are correct #5 me too. the nonzero values for f'(x) confuse me. #6 yes. That is only an approximation over an interval #8 we have dy/dx = 2f'(g)*g' so, using the product rule where y' = u*v y" = 2(f"(g)*g')*g' + 2f'(g)*g" =

posted on May 19, 2019
45. ## maths

even if f(-x) = f(x) odd if f(-x) = -f(x)

posted on May 19, 2019
46. ## math

area = base + 4 faces, right?

posted on May 19, 2019
47. ## maths

consider f(z) = e^z. then e^(x+y) = e^x e^y then g(x) = e^x/(1+e^2x) is that even or odd, or neither?

posted on May 19, 2019
48. ## maths

The axis of reflection will be midway between the two lines, right? These two lines intersect at (6,15) The axis must have y-intercept at (0,6) So, now just find the line through those two points.

posted on May 19, 2019
49. ## Calculus

#1 I get 40. How did you get 24? #2 recall that e^(lnx) = x So, you have f(x) = (x^3+5)^2 Now what is your answer? You have just said that d/dx e^u = e^u, but you forgot the chain rule. #3 That's not what I get. Let u = 1+sinθ and you have ∫ du/√u #4

posted on May 19, 2019
50. ## physics

well, the height at time t is h(t) = 0 + 60 sin42° - 4.9t^2 assuming it is hit from a height of 0 (unusual for a baseball...) anyway, if needed plug in the initial height and then just work with the quadratic function the way you remember from Algebra I

posted on May 19, 2019
51. ## pre algebra

9*19z + 9*4

posted on May 19, 2019
52. ## Maths

b-3 = 192-b 2b = 195 b = 195/2 so, a = 3 - 195/2

posted on May 19, 2019
53. ## Chemistry

Looks like it takes 5 moles of O2 to react with 1 mole of propane. So you will need 15 moles of O2. convert that to grams.

posted on May 18, 2019
54. ## calculus

for n>1, n^(-2/3) > 1/n, which sum diverges

posted on May 18, 2019
55. ## geometry

I see a line segment BD, adjacent to a 3-4-5 triangle, DCE Better ask a question and/or 'splain things better.

posted on May 18, 2019
56. ## Math

yes, b+10 = p But also, p+5 = 2e Not sure who the heck Ellis is, but if you meant Bob, then we have p+5 = 2(b+5) or, rearranging things, p - 2b = 5 p - b = 10 subtracting, we get b = 5 So, Bob is 5 and Peggy is 15 In 5 years, they will be 10 and 20

posted on May 18, 2019
57. ## math

hint: what is h(0)?

posted on May 18, 2019
58. ## math

well, the garden measures (in posts) 6x2, so now just figure the perimeter (in posts)

posted on May 18, 2019
59. ## Math

x = k + by You know that 30 = k + 2b 50 = k + 6b Now just solve for k and b, and you can answer the questions

posted on May 18, 2019
60. ## math

42

posted on May 18, 2019
61. ## Chemistry

you have 0.05246 moles of P4 the 11.54g of oxide contain 5.04 g of oxygen, which is 0.315 moles of O 0.315/0.05246 = 6 That means you get 6 moles of O for every mole of P4 See what you can do with that.

posted on May 18, 2019
62. ## Physics 20

I expect that you are to consider only the rock's horizontal speed. In that case, just recall that time = distance/speed. So, if the rock's speed was x m/s, we need the total round-trip time of rock and sound to be 4.5 s. That means we have to solve 50/x +

posted on May 18, 2019
63. ## Physics 20

those are not vector values, or even x-y coordinates. I guess you can do vectors on the number line, but that's not usually how it's done. google is your friend, and can provide many examples. as I'm sure your class text can ...

posted on May 18, 2019
64. ## Pharmacy calculations

just get out your conversion factors for changing oz and tsp to mL I assume you mean fl oz, since that is a volume unit. do the conversions, and add them up.

posted on May 18, 2019
65. ## Math

you cannot integrate sin(x^2) using elementary functions. Some numeric method is needed, or one of the special functions defined as integrals. In this case, the Fresnel Integral.

posted on May 18, 2019
66. ## Math

Draw the triangle PAB ∡B = 38° ∡A = 33° side p = 3.9 So, ∡P = 109° Using the law of sines, b/sin38° = 3.9/sin109° b = 2.54 km

posted on May 18, 2019
67. ## Maths

dx/dt = 5 dy/dt = 3x^2 dx/dt Now, the gradient is g(x) = dy/dx = 3x^2 the rate of change of the gradient is dg/dt = 6x dx/dt = 6*5 = 30 If the answer is supposed to be 3, then I must have misread the problem. O course, there's always the chance that you

posted on May 18, 2019
68. ## Maths

Draw the triangle. It has sides 5-12-13 so, csc theta = 13/5

posted on May 18, 2019
69. ## Calculus

#1 ok #2 ok #3 nope. 11/23 use implicit differentiation #4 ok #5 f = -e^x+x f' = 1-e^x f'=0 at x = 0 f(0) = -1 #6 ok #7 Nope The area is triangle+rectangle+triangle-semicircle 3 + 3 + 3/2 - 2pi = 15/2 - 2pi #8 ok #9 maybe. If that leading "-" sign belongs

posted on May 18, 2019
70. ## math

what, no calculator?

posted on May 18, 2019
71. ## Math

well, right and up are in a positive direction (add to x,y) left and down are in a negative direction (subtract from to x,y) NOW what would you say?

posted on May 17, 2019
72. ## physics

just use your basic equations of motion s = vt + 1/2 at^2 If the cop starts moving just as the car zips by, then we have the distance traveled after t seconds as car: 25t cop: 1/2 * 3 t^2 time elapsed till the cop catches up: 25t = 3/2 t^2 Now you can

posted on May 17, 2019
73. ## Math

add 6 to both sides and you get y > 18 (or y≥18 if that's what you want) In any case, the solution set is all numbers greater than (or equal to?) 18

posted on May 17, 2019
74. ## Geometry

I'm assuming that L is the slant height, so your formula for total area is correct pi R^2 + pi RL I have no idea what the "next step" is supposed to be, since you already have the total area. Is 4 the radius of some other cone, with slant height 10? If so,

posted on May 17, 2019
75. ## Geography

360°/24hr = 15°/hr so they are one time zone away. now you must decide whether they are ahead or behind ...

posted on May 17, 2019
76. ## Social studies

hmmm. you seen to have forgotten to include your choices...

posted on May 17, 2019
77. ## Math

since every number on such a cube is less than or equal to six, there's nothing else you can roll. P(

posted on May 17, 2019
78. ## math

no, it is not

posted on May 17, 2019
79. ## Math, algebra 1

if the flare burns longer than 3 seconds, it will still be burning on the way down.

posted on May 17, 2019
80. ## physics

ice-steam is 100°C 19 is 6/11 of the way from 13 to 24, so the temperature is 6/11 * 100 = 54.54°C

posted on May 17, 2019
81. ## Physics

Jack can run 780m in 60 s Zeke can run 435m in 60s 435+350 = 785 so, what do you think?

posted on May 17, 2019
82. ## math

well, it's (x+2)(x-3) / (x+2)(x) so, what do you think?

posted on May 17, 2019
83. ## math

so, how did you get 367? Maybe an obvious tweak will present itself. And what is that "x" doing in there? Is that where it belongs?

posted on May 17, 2019
84. ## math

that would of course be 5 * 2/3 = _____ jars now round down to a whole number, if that's what you want.

posted on May 17, 2019
85. ## Calculus

If you mean f(x) = ∫[x,1] √(1+t^2) dt then f'(x) = -√(1+x^2) so, f'(1) = -√2 This is just the chain rule in reverse. If F(t) = ∫f(t) dt then F'(t) = f(t) So, if u,v are functions of x, then ∫[u,v] f(t) dt = F(t) [u,v] = F(v)-F(u) Now take

posted on May 17, 2019
86. ## Chemistry

well, the ratio is 120:6 = 20:1 = 200:10

posted on May 16, 2019
87. ## Calculus help

#2 f(x) has a max where f'=0 and f" < 0 f = (x+2)(x+3)^2 f' = (1)(x+3)^2 + (x+2) * 2(x+3)*1 (product and chain rules) = (x+3)(x+3+2x+4) = 2(x+3)(x+2) = 2(x^2+5x+6) f" = 2(2x+5) So. f'=0 at x = -3, -2 f"(-3) < 0 f"(-2) > 0 so, the max is at x = -3 #3 f(x) =

posted on May 16, 2019
88. ## Algebra

posted on May 16, 2019
89. ## Math

I suspect a typo, and the last line should be 2 1 and geez, bruh, try out the rules to see which one fits, if you can't figure it out. duh!

posted on May 16, 2019
90. ## Calculus help

huh? just plug and chug If u and v are functions of x, then if y = uv y' = u'v + uv' you gotta problem with that, pal?

posted on May 16, 2019
91. ## Chemistry

240/7200 = 1:30

posted on May 16, 2019
92. ## math

hmmm. I'd say check the corresponding sides and angles ...

posted on May 16, 2019
93. ## math

No. 5P3 = 5*4*3 = 60

posted on May 16, 2019
94. ## geometry

use the law of cosines to get, say angle R. 17^2 = 10^2 + 21^2 - 2*10*21 cosR cosR = 3/5 Now find the altitude h from P using h/10 = sinR = 4/5 h = 8

posted on May 16, 2019
95. ## math

correct

posted on May 16, 2019
96. ## algerbra

5^-1 = 1/5 so, -(5)^-2 = -1/5 except for zero, anything to the zero power is 1. Think about it. x^3/x^3 = x^(3-3) = x^0 whatever number you choose, raising it (or any power of it) to the zero power just gives 1. Negative powers switch numbers from the top

posted on May 16, 2019
97. ## Algebra

y+x=3 y-2x=18 subtract the bottom from the top and you have 3x = -15 x = -5 so, y = 8

posted on May 16, 2019
98. ## algebra

√45 = √(9*5) = √9√5 = 3√5 to factor out the 3, you need to factor out √9. You just factored out √3. √45 = √3√15 √180x^2 = √(36*5x^2) = 6x√5 √250h^4 k^5 = √(25*10h^4 k^4*k) = 5h^2k^2√(10k) Interesting that you got this one

posted on May 16, 2019
99. ## physics

for each coordinate (x,y,z) find the weighted average of all the masses times their distances. For example, Mx = (5*1 + 2*1 + 3*1)/3 = 10/3 do My and Mz similarly

posted on May 16, 2019
100. ## Chemistry

how many moles NaHCO3 in 16.8 g? each mole occupies 22.4 L, right?

posted on May 16, 2019