# Posts by Alex

Total # Posts: 3,677

**Calculus**

This is actually a related rates question, so you want rates of change: so the rate of change of volume, the rate of change of surface area. This is represented as the derivative, but before you go finding the first derivative, think on how you should use the change of radius ...

*April 25, 2016*

**Calculus**

X and Y move perpedicular to each other, forming a right triangle. As such, the distance between the cars is sqrt(X^2 + Y^2), where X = +50 km/hr, Y = +60 km/hr. (These are functions.) We want the RATE at which these cars are seperating, so take the first derivative of the ...

*April 25, 2016*

**PreCal**

This set is numbers strictly greater than 2. Because this relation is strict (> instead of >=), the left interval is a parens. There is no upper bound, so the right interval is infinity. (2, +INF)

*April 25, 2016*

**PreCal**

That the price "dropped steadily" implies a linear relationship, which would simply be change in price over change in time. (140 - 90) / 5 = -$10 / week.

*April 25, 2016*

**Math**

Follow order of operations. In the first parens, 33 + 19 = 52. The second parens is 51. Our expression is now 52 * 2 * 51. Multiplication is associative, so it doesn't matter which order we do this in. My calculator gives me 5304.

*April 25, 2016*

**Algebra**

I'm getting D.

*April 25, 2016*

**cs 2**

Which part of this assignment are you having trouble with? The logic? Or File I/O?

*April 24, 2016*

**statistics**

The problem wants the test statistic for a one-proportion z-test, which we know because we're only given data for 1 test and that "492 / 806" implies a proportion. The sample statistic for this test is given by sqrt(pq / n). p = 492/806 (probability of success) q...

*April 24, 2016*

**statistics**

So the population distribution-- the distribution of ALL M&Ms-- is given in the problem: N(0.8565, 0.0518). However, we want to know what the mean weight will be if, instead of pulling from ALL M&Ms, we "randomly select 465 M&M plain candies." This is our sample. ...

*April 24, 2016*

**statistics**

You are given a normal distribution of a population. You want to know things about a sample distribution, so you should start with constructing a normal distribution for your sample of 465 M&Ms. The mean of this sample remains the same. The standard deviation is the population...

*April 24, 2016*

**statistics**

The normal distribution is N(25, 10). P(X > 20) = .691 So approximately 69.1% passed the exam. 69.1% of 100 students is 69 students.

*April 24, 2016*

**geometry (check my answers)**

All statements are true. A rectangle simply requires that a four-edged figure has 4 right angles and two sets of parallel lines. A square is a special case-- that all four sides are the same length, but it's still a rectangle. The rest of your answers are correct. :-) It ...

*April 22, 2016*

**math**

What's the question?

*April 22, 2016*

**physics**

Er, what's the question?

*April 21, 2016*

**math**

y = -x + 8. (7, 1) corresponds to (x, y), so just plug in the values into the equations and see which one works. For the above equation, 1 = -(7) + 8 1 = 1 This is true, so this is indeed the correct equation.

*April 21, 2016*

**math**

Yes, quadrant IV is correct. :-)

*April 21, 2016*

**Sampling Distributions**

A - The sample standard deviation is the population standard deviation over the square root of the sample size, 30 / sqrt(36). The mean of an approximately normal sample distribution is the same as the population mean, so the sample distribution is N(360, 5). B - If you want ...

*April 21, 2016*

**stat**

We construct a binomial distribution. The probability of "success" (a substandard rod) is .05. We have 300 trials. B(.05, 300) P(X < 20) = .881

*April 21, 2016*

**Physics**

First convert your angular speed from rpm to rad/s. You can then convert your angular speed to tangential speed with v = omega * r. (Be sure to convert that diameter into SI units!) Newton's second law gives us F = ma, where this is centripetal acceleration, so F = (mv^2)/...

*April 21, 2016*

**math**

Sure, sounds good to me. :-)

*April 21, 2016*

**math**

I don't understand the question?

*April 21, 2016*

**Bio**

Because unique identifiers mean that, given a name, someone could find out about the organism. If we had two things with the scientific name "cat," that would be a problem-- there are tons of cats. But since no two species of cats have the same two names, given a ...

*April 21, 2016*

**Bio**

Ah, but each scientific name is unique. Chip brand names may be ridiculous-- Lay's, Doritos, Cheetos, etc.-- but they're unique so they still serve as good identifiers. (Can you tell I'm sitting next to a vending machine?) (Fun fact, ursus is also Latin-- most ...

*April 21, 2016*

**Bio**

D. All scientific names identify an organism's genus and species. Usually this name is Latinate (interesting-ish story involving Linnaeus), though it doesn't have to be.

*April 21, 2016*

**Geometry**

That's not a math error, that's a conversion error. Answers are in yards, lengths are given in feet. Cheap trick-- I just noticed it myself.

*April 21, 2016*

**Geometry**

Are you told that this is a right triangle? If you aren't, you'll have to law of cosines for the length of the third side. You could then Heron's for the area.

*April 21, 2016*

**Statistics**

I would say A, though that's because I was taught an 8-part procedure for hypothesis testing, and B - D are their own separate steps. It does make sense that you'd define your hypotheses in the hypothesis step, though, and you really shouldn't be calculating the ...

*April 21, 2016*

**Educational Technology**

I agree with all three of your answers. :-)

*April 20, 2016*

**Language arts**

Without the passage, it's difficult to discern anything about questions 1-3. 4, however, should be D. The way the sentence is set up is to imply a contradiction, something like "Geese usually fly in a V formation but they aren't today." Unpredictable ...

*April 20, 2016*

**Math**

Here, let's define "success" to be that the plant doesn't grow. This would be 1 - .6 = .4. We construct a binomial distributions with 6 trials (6 seeds planted). We want 4 events. B(6, .4) P(X = 4) = .138

*April 20, 2016*

**HELP PHYSICS PLS :)**

This is a perfectly inelastic collision, so we know that energy is conserved. (Good job identifying the problem!) Assuming you choose your "0" PE point to be the bullet's initial height: E(i) = E(f) .5m(bullet)v(bullet)^2 = m(tot)gh(system), where h is the height...

*April 20, 2016*

**Math PLZZZ HELP!!!**

I'd go with the second and third choices. That the scatter plot has a positive trend tells you that you have a line of best fit with a positive slope. This satisfies both the second and third statements. The first answer assumes that all points on the graph fall exactly on...

*April 20, 2016*

**Math**

Multiply both sides of the inequality by 2. x <= -30, which is D.

*April 20, 2016*

**Math**

Are you sure that's all the data and that you typed that data in correctly? I haven't thrown this into my calculator, but just by observation, the range would be 27 - -52 = 79? None of those choices are correct if that's your complete data... (If you have to pick, ...

*April 20, 2016*

**Physics**

Let's start by converting everything to SI units. 15 m/hr/s = 6.71 m/s/s 65 m/hr = 29.1 m/s We have constant acceleration, so we can use our constant acceleration kinematic formulas. Here we initial velocity, final velocity, acceleration, and want time so we use v(f) = v(i...

*April 20, 2016*

**Statistics**

The probability of our event occurring is .8. We construct a binomial distribution, with 4 trials, of which we want 3 to occur. B(4, .8) P(3) = .4096

*April 19, 2016*

**Math**

Multiply both sides by 3729, yielding 3729tan(7)

*April 19, 2016*

**Math**

Actually, wait. You should be using tan, since you're given the adjacent side. (The lesson here: always draw a picture.) 120tan(36).

*April 19, 2016*

**Math**

The transit here is extraneous information-- it's simply a device used to measure angles (I assume). We know that the base of the right triangle is 120 feet. (Notice that the transit of 8ft is nonsensical in this problem doesn't make sense because we're solving for...

*April 19, 2016*

**Math**

Perimeter is the sum of all sides. For a rectangle, P = 120 = 2L + 2W. You are given that L = 3n W = n, so you can now do a substitution into the perimeter equation: 120 = 2(3n) + 2(n). Simplifying this, we get 120 = 8n, so n = 15. Revisiting our length and width equations, L...

*April 19, 2016*

**Math**

1/15.5 = 2/31

*April 18, 2016*

**computer science**

What specific part are you having trouble with? The packages? File I/O? What language?

*April 18, 2016*

**calculus**

Between y = 2x2 + 9x − 4 and y = −x2 + 6x + 2 for x in [−2, 2]

*April 18, 2016*

**Language Arts**

You are correct. :-) A conjunction joins two parts of a sentence together. A better example to describe this would be "Alice bought a calculator, and Ben bought a mouse." The conjunction "and" divides the sentence into two thoughts-- "Alice bought a ...

*April 18, 2016*

**math**

Set up a proportion: If Bill can type 10 pages in 24 minutes and we want to know how many pages he can do in 5.5 hours (330 minutes), a possible proportion is: 24/10 = 330/x Cross-multiplying we get 24x = 3300, so x = 3300/24 = 138 pages.

*April 17, 2016*

**Algebra**

The easiest way to justify this is to visualize the graph. We know from the first the signs of this equation that this quadratic opens upwards and know that it is shifted to be above the x-axis, so the quadratic never crosses the x-axis and therefore has no roots. You could ...

*April 17, 2016*

**Math grade 7**

Net daily change is revenue - expenditures, 12500 - 15000 = -2500. The overall change in the treasury's funds is 1.1Mil - 1Mil = 100K. To find out how many days, we divide the overall change by the net daily change in revenue: 100K / 2500 = 40 days.

*April 15, 2016*

**Translating a sentence into a one-step equation**

60 = v - 13

*April 15, 2016*

**Algebra 2**

If it's multiple choice, plug and chug those points. Otherwise, you have two options: 1) Quadratic Regression 2) Conics I opt for quadratic regression given that I've not done conics in three years, lol f(x) = -x^2 + 5x -4

*April 15, 2016*

**Translating a sentence into a one-step equation**

g + 17 = 46

*April 15, 2016*

**Reverse math confused**

Her preliminary cost (prior to tax and tip) is regular price (p) - 2. Tax and tip is 20% of this preliminary cost, so total cost is 9 = 1.2(p - 2). p = $9.50. (Nice coupon, there...)

*April 15, 2016*

**Math**

We know that after cutting 1/3 of the coil and 8m of the coil, 1/2 of the coil remains. This can be written as 1/3 + x = 1/2, where x will be 1/6. We know that this 1/6 of the coil is 8m, so the total length of the coil is 8 * 6 = 48m because one coil = 6 subcoils each of 8m.

*April 14, 2016*

**physics**

Where is Q located? I'll explain how to do this, since I don't know enough about this problem. Solve for the the bob's velocity right before it hits ball Q using energy equations: U(bob) = KE(bob) + U(Q). From here you can use your elastic equations to solve for ...

*April 14, 2016*

**math**

The volume of the tank is 3885 cubic centimeters. Volume is equivalent to length * width * height, in which you are provided both length and width. Your equation becomes 3885 = 18.5 * 15 * height Solving this, we get height = 14 cm.

*April 14, 2016*

**Quadratic Equations**

A quadratic equation's shape is a parabola. So anything with a curved trajectory would fit: throwing a ball / javelin / football / anything, shooting an arrow... Here's a fun picture: prntscr . com / arm214

*April 13, 2016*

**test corrections for problems 6,11,12 and 23please**

We want f(x) - g(x) and are given both equations. All you have to do is substitute: 9x^3=2x^2-5x+5 - (5x^3-7x+4) Be sure to distribute that negative sign! (I'd give you an answer but I'm not sure what that equals sign is supposed to be?)

*April 13, 2016*

**test corrections for problems 6,11,12 and 23please**

The sphere question is very similar to the cylinder question. Stick the provided value r into the provided surface area equation. SA = 4pi(2x+5)^2 Here you distribute / foil (2x+5) out when expanding, yielding 4pi(4x^2 + 20x + 25). Again, you should multiply each term by 4pi ...

*April 13, 2016*

**test corrections for problems 6,11,12 and 23please**

Oops. Add an x^2 to my previous answer. I wasn't sure why we had random x's in the problem, so I just dropped them. You're given the radius and the height of the cylinder. Simply stick in the given values into the provided formula and solve, yielding pi(80x^4 + 64x...

*April 13, 2016*

**test corrections for problems 6,11,12 and 23please**

A picture is helpful. Start by drawing the 8 by 12 lot. The field must fit in this lot and is 3 by 6. The area that is not the field is the remaining area. This is a simple area calculation. Total area of the lot is 8 * 12 minus the area of the field, 3 * 6. The remaining area...

*April 13, 2016*

**Math**

Yes, 76%.

*April 13, 2016*

**Integers**

From the problem statement, we know that some 6 integers must sum to 171. To get an idea of what these numbers are, start by dividing 171 by 6. This yields 28.5, which is what the average of our numbers are. Here we can construct numbers close to this interval-- the problem ...

*April 12, 2016*

**Maxima and minima Application**

This is a parabola, so it can either open upwards and have a min but not a max or open downwards and have a max but not a min. From the sign of the leading term (+1), we know this opens up. The minimum position of this parabola would be the point of symmetry. To find this, we ...

*April 12, 2016*

**math**

From the prompt, we know that: a) L = W + 2 b) Perimeter = 28 = 2L + 2W Where I call breadth W The easiest way to solve this system is by substitution. Plug in (a)'s value of L into b, yielding 28 = 2(W+2) + 2W. From here, isolate and solve for W. You should get W = 6cm. ...

*April 12, 2016*

**Math**

1) Picture the equation. It must decrease at an unknown rate, then flatten out as it nears 60K (asymptote). This would be in the family of functions of 1/x because 1/x is the most common function to have asymptotes, which Google seems to call power / reciprocal / rational / ...

*April 12, 2016*

**Math**

175 / 625 = 28% (What kind of party lasts 6 hours?)

*April 12, 2016*

**Math**

Only a dilation would change the shape's dimensions-- any type of shift would simply relocate the shape. We must only prove that dilation do not change the concurrency. Dilations, by definition scale on object-- if you dilate it by 2, the second image will be exactly twice...

*April 12, 2016*

**Science**

A - True. B - False. ATP -> ADP releases energy. C - False. ADP -> ATP represents storing energy. (Also you can't "break down" ADP into ATP.) D - False. Glucose and ADP / ATP can both store energy.

*April 12, 2016*

**physics**

A) This is a conservation of energy problem, so E(i) = E(f). I'll pick our point of origin to be the spring's equilibrium height-- this makes the gravitational potential energy of the ball easy to calculate. We now identify what types of energy are present at the ...

*April 12, 2016*

**Math**

Start by calculating the area of the desk. Area of a rectangle is base x height, 5.5 * 3.5 = 19.25 ft^2. Now calculate the area of the tile: .5 * .5 = .25 ft^2. To figure out how many tiles can fit, divide the area of the desk by the area of one tile: 19.25 / .25 = 77 tiles.

*April 12, 2016*

**math polynomials**

I'm assuming you're solving for x? Set each term in parentheses equal to 0, yielding: ~ 3x + 4 = 0 ~ x - 2 = 0 Now isolate x and solve. For the first equation, this would be subtracting 4 from both sides, then dividing by three. x = -4/3, 2

*April 12, 2016*

**PHYSICS Momentum!! Collision HELP**

Your assumption is correct. If you simply choose initial to be "before the collision," a) P(iA) = 0.202 * 2 P(iB) = 0 b) KE(iA) = .5 * .202 * (2)^2 KE(iB) = 0

*April 12, 2016*

**Linear Algebra**

p1, p2, p3 are elements of P_2 p1(x)= 1+x-2*x^2 p2(x)= 2+3x-x^2 p3(x)= 3+5x-x^2 Is S = {p1, p2, p3} linearly independent?

*April 10, 2016*

**math**

Take natural log of both sides. therefore ln(15)=ln(2^x) move x to the front ln(15)=x*ln(2) move ln(2) to the other side therfore x=ln(15)/ln(2) write all this down on paper to see it properly.

*April 10, 2016*

**Algebra**

A basketball player makes 53 points on 24 shots. How many 3 pointers and 2 pointers did he shoot. Show your work. I know that the answer is 5 for the 3 pointers and 19 2 pointers but I don't know how to show it.

*April 7, 2016*

**Science**

PLEASE HELP 1. Katie is bowling. She starts with the ball in her right hand and her arm as far back as it will go. She swings the ball forward, applying a force of 78 Newtons the whole time. When her hand has traveled through a path of 0.9 meters, she releases the ball, and it...

*April 4, 2016*

**Chemistry**

What is the pH of the solution when 50.00 mL of 0.250 M HNO3, nitric acid, has been treated with 25.00 mL of 0.400 M NaOH? Below is the work I performed, however, my professor deemed the [H3O] as incorrect. Where did I go wrong? [NaOH] = .025 L x 0.400 M = .010 mol [HNO3] = ....

*March 30, 2016*

**Derulo**

13 more than the product of M & 5

*March 29, 2016*

**Check my answers for world history please!**

Good

*March 29, 2016*

**The 5th Wave**

Yes yes and yes

*March 29, 2016*

**math**

All of these answers are wrong, the real answer is 9 because: 36*0.2(20%)=7.2, this is how much water the berries obtain. Now you do 7.2 divided by 0.8 which equals 9 -you do this step to find out how much water and the rest of the stuff in the berries. By the way i'm in ...

*March 27, 2016*

**math**

Marcela 27 donuts from Dunkin Donuts. She ate one ninth of the donuts. She took the remaining donuts and shared them equally amongst 12 classmates. How many donuts did each friend receive?

*March 21, 2016*

**math**

Marcela 527 donuts from Dunkin Donuts. She ate one ninth of the donuts. She took the remaining donuts and shared them equally amongst 12 classmates. How many donuts did each friend receive?

*March 21, 2016*

**math**

Alex bought 27 donuts from Dunkin Donuts. He ate 1/9 of the doughnuts. He took the remaining donuts and share them equally amongst 12 classmates. How many donuts did each friend receive?

*March 21, 2016*

**Business**

1. c 2. c 3. b 4. b 5. b 6. c 7. a 8. b 9. c 10. d 11. a 12. c 13. d 14. a 15. c 16. a 17. c 18. a 19. d 20. d I got 100%

*March 19, 2016*

**Math**

A hospital was out of juice at the end of September. They bought 200 cases on October 1 at $10/each and 200 more cases on November 1 at $12. There were 100 cases left at the end of October. What is the total of the first case expensed on November 2nd?

*March 18, 2016*

**Math**

A hospital was out of juice at the end of September. They bought 200 cases on October 1 at $10/each and 200 more cases on November 1 at $12. There were 100 cases left at the end of October. What is the total of the first scare expensed on November 2nd?

*March 18, 2016*

**Science**

thanks i got a 100%

*March 17, 2016*

**math**

wow

*March 15, 2016*

**Physics**

A body of mass 10g oscillates with Simple Harmonic Motion of amplitude 4cm and time period 0.50s. Calculate: a) The maximum acceleration. b) The maximum kinetic energy.

*March 13, 2016*

**Spanish**

2)descanso 3)retirarse 4)madrileños

*March 12, 2016*

**math**

Deloris is wrong, its 956.5

*March 8, 2016*

**intro to physic fundamentals**

the speed of a roller coaster that had descended 29.0 m was only slightly greater when it had an initial speed of 5.00 m/s than when it started from rest. This implies that ΔPE KEi. Confirm this statement by taking the ratio of ΔPE to KEi. (Note that mass cancels.)

*March 4, 2016*

**phliosophy( justifying using the rule of inference**

1.) A > B 2.) B > C 3.) ~C.D //:. ~A

*March 2, 2016*

**trigonometry (Course and Bearing)**

how do you sketch this kind of problem?, that's the reason why i'm having trouble with this ..

*March 2, 2016*

**trigonometry (Course and Bearing)**

two lighthouses are situated such that B is 7 km directly east of lighthouse A. A ship at point P observes that A is due north and that the bearing of B is 46°10'. How far is the ship from A and B ?

*March 2, 2016*

**Social Studies**

I think so. wait to see what reed says

*March 1, 2016*

**Social Studies**

its not my social studies. it is Ann

*March 1, 2016*

**Social Studies**

The 1868 state constitution for South Carolina was revolutionary because it embodied many democratic principles absent from previous constitutions. The new document provided for population alone, rather than wealth or the combination of wealth and population, as the basis for ...

*March 1, 2016*

**Geography and Society**

Without the atmosphere that protects the Earth, humans, animals and all plant life would not be able to survive. The atmosphere works to hold oxygen in the area around the earth. Humans and most animals are dependent on oxygen. Plants are also dependent on oxygen because they ...

*March 1, 2016*

**Math**

I'm a student

*March 1, 2016*