Homework Help Thread--SPLIT

[cipher_text]

and now for some math

How many litres of pure (100%) alcohol must be added to 30 litres of a 50% alcohol concentration in order to raise it to a 62.5% alcohol concentration??

All i could think of :

x = # of litres of 100% alcohol
y = # of litres of 50% alcohol
z = # of litres of 62.5% alcohol

x + y = 30

.625 (30 + x ) = z

The answer is 10.
But, I cant seem to be getting the equations right.

Someone please aide moi !!

[pipsqueeek]

You've got 30 liters 50% alcohol, or 30(.5), which you are adding to x liters of 100% alcohol, or x(1), which then gets you 30+x liters of 62.5% alcohol. Putting that all together you get

30(.5)+x = .625(x+30)

From there you just have to solve for x.
I hope that made sense. I'm not sure how coherent I am at half past midnight.

[Jocelyn Spicer]

Drat! I would have used this thread for help on The Roman churches and why the Roman Catholic and Orthodox churches split, but I didn't join quick enough! Oh well. I'll use it on something else.

[Carson]

I need some information on the decline of the Qing dynasty. Basically anything after the Taiping rebellion any help would be appreciated.

[jellyoflight]

What are the advantages of testing cosmetics on animals?

[fzun]

I really need help with my trigonomoetry homework.
Verify that the two equations are identities.

tan^2x-sin^2x=tan^2xsin^2x

The only difference is the - on the left, only allowed to work one side of the equation to solve. I have no clue what to do, help?

Also,

(1-2cos^2x)/(sin^xcos^x)=tan^x-cot^x
the ()/() is a big fraction. I need to get one of the sides to look like the other, agian only working one side.

Anyone who can figure it out will totally be my hero forever!

What are the advantages of testing cosmetics on animals?

You're not damaging any humans in the process. Although that's not much of a reason, researchers clearly value human life over animal life. If they can observe how cosmetics react on animals they can predict what will happen on humans.

[Yoshi]

fzun:

1. I'm using the right side.

(tan²x) (sin²x)
=(sin²x/cos²x) (sin²x)
=(sin²x/cos²x) (1-cos²x)
=(sin²x/cos²x) - sin²x
=tan²x - sin²x

2. I'm confused by your notation..."sin^x" doesn't make sense. I'm assuming you mean "sin x" and likewise for the other ones? Anyway, I'm using the right side again.

tan x - cot x
=(sin x/cos x) - (cos x/sin x)

Place them under a common denominator:
=(sin²x - cos²x) / ((sin x)(cos x))
=((1 - cos²x) - cos²x) / ((sin x)(cos x))
=(1 - 2cos²x) / ((sin x)(cos x))

[Experiment]

Well, I've got some linear algebra (matrices) questions for you all, I'm good with solving problems, but for once, I'm bad with the fundamental concepts

1. Mark each statement true or false, and justify each answer
a. Not every linear transformation from R[sup]n[/sup] to R[sup]m[/sup] is a matrix transformation.
b. The columns of the standard matrix for a linear transformation from R[sup]n[/sup] to R[sup]m[/sup] are the images of the columns of the n x n identity matrix.
c. I've got this one, no worries.
d. A mapping T:R[sup]n[/sup] --> R[sup]m[/sup] is one-to-one if each vector in R[sup]n[/sup] maps onto a unique vector in R[sup]m[/sup].
e. If A is a 3 x 2 matrix, then the transformation x |--> Ax cannot map R[sup]2[/sup] onto R[sup]3[/sup].

There's another question, but it'd be a pain to write out and explain, so I'll just solve it on my own then. Thanks in advance!

EDIT: Dangit, just pretend those sup tags means something is in superscript. How'd you pull off your superscripts Yoshi?

[Anoohilator]

ALT + 0178 = ²
ALT + 0179 = ³

[shapu]

What are the advantages of testing cosmetics on animals?

Well, while I'm fundamentally opposed to the idea, here are a few:

Most mammals have pretty similar eyes to ours. Thus, testing cosmetics near the eyes of animals helps us to determine the reactions of human eyes to cosmetics.

Laboratory animals are cheaper than people to keep an eye on and can be kept in the same place for days/weeks/months, allowing for better viewing of effects of cosmetics on them. Also, they can't lie and tell you they did or didn't wash something off, when they didn't or did.

Lab animals never sue you.

[pipsqueeek]

Anyone speak french?

I need to know how to say move, as in, when I was two my family moved from Colorado to Nebraska.

Thanks in advance
(more to come most likely as I continue trying to write my 'essay')

Edit// How would I say 'when I was almost three'? I don't know how to say almost.
// What word would you use for little in 'when I was little'? Would it be petite, jeune, or something else?
// Is tooth fairy just fée de dents, or something else? And for saying that I though she was real, what word would I use for real?
// What about 'The Easter Bunny' and 'either' (I didn't believe in the easter bunny either)

Next day edit// And there's more!
How would you say acted(in a play)
Encore can be used to mean still, right(I still sing)? Does it come before the verb or after?
// How would you say anymore(as in I don't ___ anymore)?
// For 'I started playing the piano', would it be j'ai commencé + de + infinitive or just j'ai commencé + infinitive? Or something else entirely?
// Is a grade in school a catégorie? And so, would third grade be la troisième catégorie? And for to be in third grade would you use dans or something else?
// Is half a year un demi-an?
// A few more, then I think I'm done.
What word would I use for grumpy(if someone was just generally a grumpy person)?
I know that if you have pas, articles get changed to de. Is this the same with other negation words(mot sure what else to call them) or would I leave it as des?

If anyone can help me I would love them forever.

[Hunter Lupe]

The chance of Bob forgetting an umbrella in a shop is 1 / 3. After visiting 2 shops, Bob is no longer in possession of his umbrella. What is the probability that he left it in the second shop he visisted?

It's a somewhat simple question, but nevertheless...

[Bangel]

The chance of Bob forgetting an umbrella in a shop is 1 / 3. After visiting 2 shops, Bob is no longer in possession of his umbrella. What is the probability that he left it in the second shop he visisted?

It's a somewhat simple question, but nevertheless... ;)

Okay. Bob goes to store number 1. The chance he loses it is 1/3. The chance he doesn't lose it is 2/3. Now let's say he lost it in store number 1. Bob goes to store number 2. The chance he loses it is 0- he already lost it. The chance he doesn't lose it is 1. Now, let's say he didn't lose it in store number one. The chances for store number two are the same. The chance he loses it is 1/3, the chance he doesn't lose it is 2/3.

So the total chance: 2/3 he doesn't lose it in first * 1/3 he does lose it in second = 2/9.

scottnak helped.

[pipsqueeek]

The chance of Bob forgetting an umbrella in a shop is 1 / 3. After visiting 2 shops, Bob is no longer in possession of his umbrella. What is the probability that he left it in the second shop he visisted?

It's a somewhat simple question, but nevertheless...

Okay. Bob goes to store number 1. The chance he loses it is 1/3. The chance he doesn't lose it is 2/3. Now let's say he lost it in store number 1. Bob goes to store number 2. The chance he loses it is 0- he already lost it. The chance he doesn't lose it is 1. Now, let's say he didn't lose it in store number one. The chances for store number two are the same. The chance he loses it is 1/3, the chance he doesn't lose it is 2/3.

So the total chance: 2/3 he doesn't lose it in first * 1/3 he does lose it in second = 2/9.

scottnak helped.

I don't think you have to multiply by 1/3 at the end. Because if he doesn't lose it in the first he has to lose it in the second.


Edit// Gah! What's that word. So I've got the sentence "...and a strong ___ on horses.", meaning that horses were important and they valued them and all that, but I can't for the life of me think of the word that goes in the blank! Anyone having a better time remembering what I was thinking that I am?

[shapu]

emphasis.