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[Takuya]

That is correct (I think)! I really need to practice my basic math logic more. I was think too much into it, adding the areas using their diameters <.<;

EDIT: or rather, (pi)r^2, etc.
EDIT 2: Not really sure whether diameters can be figured in for square inches, but... idk.

 

[stephaknee]

The answer may have been right, but Marly wrongly used the diameter as the the sq in. You have to find the area with the diameters given.

 

[Takuya]

Edited that into my previous post. Instead of adding together the diameters, it should be sq. inches.

EDIT: Second note; for this question, competitors weren't allowed calculators.

 

[stephaknee]

To answer your second edit.

A = PR^2
R = D/2.

 

[Takuya]

After a couple of minutes with notepad and calculator, I got

A: ((pi)6^2 + (pi)8^2)/13 = 24.166
B: 2((pi)8^2)/14 = 16.157
C: (pi)10^2/15 = 20.944

So it should be ranked - BCA


<_< Now to do this without a calculator.

 

[stephaknee]

After a couple of minutes with notepad and calculator, I got

A: ((pi)6^2 + (pi)8^2)/13 = 24.166
B: 2((pi)8^2)/14 = 16.157
C: (pi)10^2/15 = 20.944

So it should be ranked - BCA


<_< Now to do this without a calculator.

Leave in terms of pi

A: 36pi + 64 pi = 100/13 pi = 7 + 9/13 pi.
B: 64 pi + 64 pi = 128 pi / 14 = 9 + 1/7 pi
C: 100/15 = 6 2/3 pi

So its BAC. Like I said early, marly got the right answer, but didn't do it in the way the question asked.

 

[Takuya]

Leave in terms of pi

A: 36pi + 64 pi = 100/13 pi = 7 + 9/13 pi.
B: 64 pi + 64 pi = 128 pi / 14 = 9 + 1/7 pi
C: 100/15 = 6 2/3 pi

So its BAC. Like I said early, marly got the right answer, but didn't do it in the way the question asked.

*CAB

Ranked from least to greatest. But that's right.

Now, a simple question: How does

_1_
√2

equal 2^(-1/2)?

 

[Eternal Redemption]

*CAB

Ranked from least to greatest. But that's right.

Now, a simple question: How does

_1_
√2

equal 2^(-1/2)?

x^1/2=Square root of x. So 2^1/2 = square root of 2. Negative powers are reciprocals. So you flip it upside down and get :
_1_
√2

 

[Vayne Mechanics]

*CAB

Ranked from least to greatest. But that's right.

Now, a simple question: How does

_1_
√2

equal 2^(-1/2)?

Another way to write the square root of a number, say x, is x^(1/2).

Now, when you have a fraction where it's 1/x, you can depict x in terms of exponents. 1/x is equivalent to x^(-1)

So if you have 1/√x, then you have 1/x^(1/2) but you also know that 1/x is x^(-1), so then 1/x^(1/2) is equivalent to x^(-1/2)

In this question, x would have a value of 2.

 

[Eternal Redemption]

Another way to write the square root of a number, say x, is x^(1/2).

Now, when you have a fraction where it's 1/x, you can depict x in terms of exponents. 1/x is equivalent to x^(-1)

So if you have 1/√x, then you have 1/x^(1/2) but you also know that 1/x is x^(-1), so then 1/x^(1/2) is equivalent to x^(-1/2)

In this question, x would have a value of 2.

Agreed. Refine what I said into this. :/

 

[Takuya]

:l Asked my math teacher how

5^log2 + 2^log5 - 50^log2 = 0 With logs having the base of 10.

She couldn't come up with anything. Referred to a calculus teacher who happened to walk by the door in the hallway.

He couldn't come up with anything. Told me he would think about it for 5 minutes. Couldn't solve it.

The problem is from the 1997 math competition.

 

[Oracle Spockanort]

I'm taking Beginning Japanese at my college right now and we don't learn sh!t. I do not get how to phrase a certain question. Like if I ask:

どこに　いくますか。　（Doko ni ikimasu ka.) would that be correct if I want to ask where are you gong?

and if I want to ask with who are you going with would it be:

だれと　いきますか。 (Dare to ikimasu ka.) is that right?

And why does や let you only include two things when you are taking about objects. Like みずうみや　温泉　あります。 We haven't learned why certain particles modify in certain ways yet...and how each particle modifies. We just know they are there.

 

[AxelRoxasFan223]

AxelRoxasFan223
Areas of Expertise:
Biology
Geography

and i suck at math xD
Yay a homework help thread xD

Oh and im still just in school not college yet

 

[stephaknee]

Hoping someone who's good at statistics is online. ;_;

n = 175

x mean: 57.7
x standard deviation: 3.8

y mean: 59.8
y standard deviation: 19.5

The point estimate for the correlation between x and y is .36 (p=0.0001). Is there evidence for significant correlation between age and severity score among all patients?

Yea I have no idea what the point estimate or p=0.0001 means. I think the p is supposed to be rho, though.

[edit] okay so I thought maybe the point estimate is the sample correlation coefficient? (r-value?) and that p=.0001 might just be extraneous information. If anyone can verify/say no wtf you're retarded that would be helpful. ;[

 

[Nostalgia]

I need help with a torque problem from my physics class. I attempted to do it, and my numbers, though reasonable, do not add up as they should. I'm hoping that if I describe the process step-by-step, someone could show me where I went wrong.

Here's the actual problem:

An 850.0N painter stands 1.2m from one end of a 3.00m scaffold supported at each end by a stepladder. The scaffold weighs 250.0N and there is a 40.0N can of paint 0.50m from the end opposite the painter. How much force is exerted by each stepladder?

I drew a picture to use as a reference. (Please forgive the sloppiness of the picture; it was done in Microsoft Paint, lol.)

This sort of problem is a bit trickier than the ones I'm used to because we're dealing with two supporting objects, and each exerts a different amount of force. My teacher suggested that we take out one of the stepladders in order to focus on calculating the force for one.

So, I placed my pivot point all the way at 0.0m (from the left of the scaffold). I ignored F1 so that I could focus on F2, which is on the opposite side of the pivot. (By the way, the red triangle represents the pivot point.)
'
With that in mind, I wanted to find the total force exerted upward and downward because finding F2 and subtracting it from the total force (or Ft for the rest of this problem) should give me F1, no?

I then used this equation.

(850N)(1.2m) + (250N)(1.5m) + (40N)(2.5m) = Ft = F1 + F2.

My result was shockingly an even 1495N of Torque (which I just checked again as I typed this out).

As for F2, I assumed that its torque force x 3m should equal 1495. So, I divided 1495 by 3, and got approx. 498.33N. Subtracting that from the total force should get me F1, but I decided to check the answer by changing the pivot point to the other side and I set up the equation in favor of F1 instead.

So, I put into the calculator the following:

(40N)(.5m) + (250N)(1.5m) + (850N)(1.8m)

That comes out to be 1075, which is strange enough. 1075/3 is approx. 358.33, and that obviously doesn't make 1475 or 1075 when combined with 498.33.




I just realized that this drawing is not very proportional, unless the painter is the size of an infant, lol.
Sorry for the lengthy explanation, but I'd really appreciate if someone could tell me where I went wrong. Thanks in advance!

 

[Vossler]

Alright I suck at Geometry. I am failing Geometry. I need help with the patagroem theory or whatever the hell it is called.

I know the basic standards of it all (all I know is it is a-squared+b-squared=c-squared)

We are using that with Triangles. They give us a triangle where the legs are given, and then there is an X or some other variable. How do I use the Patagoream theory to solve the triangles Area.

 

[Nostalgia]

What are the lengths given? Also, is it a right triangle?

 

[Vossler]

Alright new problem same theory I mentioned earlier, but this time it is a word problem.

Here is the problem.

A 480inch wide screen television means that the measure along the diagonal is 48-inches. If the screen is a square, what are the dimensions of the length and width?

The instructions for this problem are as follow.

Solve. Round your answer to the nearest tenth.

 

[Nostalgia]

Well, to start things off, you have to understand that because we're dealing with a square, both legs of the triangle will be equal. The hypotenuse will be that diagonal measurement of 48 in.

This should help.

a^2 + b^2 = c^2, as you know.

But, in this case, a = b, so a^2 = b^2. With that in mind, you can actually write a^2 + b^2 as 2x, because it's 2 multiplied by that number, which is the length of the leg.

Next, we have to find c^2. c = 48, so square 48, which comes out to be 2304.

If a^2 + b^2 = c^2, a^2 + b^2 = 2x, and c^2 = 2304, then we can substitute those new figures in to say that 2x = 2304. Algebraically, x then = 1152. But, 1152 is a^2 or b^2, so you have to take the square root, which comes out to be positive 33.9 (when rounded to the nearest tenth).

Sorry if it seems like a long and annoying process, but it becomes easy once you visualize it.

 

[JuttingRock]

So, I placed my pivot point all the way at 0.0m (from the left of the scaffold). I ignored F1 so that I could focus on F2, which is on the opposite side of the pivot. (By the way, the red triangle represents the pivot point.)
'
With that in mind, I wanted to find the total force exerted upward and downward because finding F2 and subtracting it from the total force (or Ft for the rest of this problem) should give me F1, no?

I then used this equation.

(850N)(1.2m) + (250N)(1.5m) + (40N)(2.5m) = Ft = F1 + F2.

My result was shockingly an even 1495N of Torque (which I just checked again as I typed this out).

You need to be extremely careful of units, 1495 is the correct value of the moment not force. Moment is designated with units of N*m (Newton-meters), whereas force is in units of N (Newtons), so it's considered "bad notation" to say "so and so Newtons of Torque". If you keep track of your units, it can make troubleshooting problems really easy. Just for future reference.

As for F2, I assumed that its torque force x 3m should equal 1495. So, I divided 1495 by 3, and got approx. 498.33N. Subtracting that from the total force should get me F1, but I decided to check the answer by changing the pivot point to the other side and I set up the equation in favor of F1 instead.

So, I put into the calculator the following:

(40N)(.5m) + (250N)(1.5m) + (850N)(1.8m)

That comes out to be 1075, which is strange enough. 1075/3 is approx. 358.33,

Your method is correct, but when I do the math I get a different number, not 1075, so you may have just entered it into your calculator weird.

and that obviously doesn't make 1475 or 1075 when combined with 498.33.

When you do this final check make absolutely sure that your units agree. As I mentioned earlier, this will save a lot of headaches. Because the 498.33 is in units of N, whereas the 1475 is in units of N*m, they won't work out right when you try to set them equal to each other.

If you add F1 and F2 together they should equal the total force felt by the scaffold (the person, the paint and the weight of the scaffold itself), 1475 and 1075 are in units of torque.

F1 + F2 = 40N + 250N + 850N

Good luck!