8th grade math help

[jibij]

Trying to help out the kid, but math and I never got along.

If I have a 30% solution and a 5% solution, how do I create 35ml of a 12% solution from them?

[brice618]

i feel stupid, i can't figure it out! glad i'm not in a math related field

[spanky]

Trying to help out the kid, but math and I never got along.

If I have a 30% solution and a 5% solution, how do I create 35ml of a 12% solution from them?

Looks like 2 equations and 2 unknowns...

30x + 5y = 12
x + y = 35

[72Twenty]

Right now I am watching A Few Dollars More. I wonder how Clint Eastwood would answer this question....

[nhtele]

Trying to help out the kid, but math and I never got along.

If I have a 30% solution and a 5% solution, how do I create 35ml of a 12% solution from them?

.3*x + .05*(35-x) = .12*35

Solve for x, where x is the volume of the 30% solution. Should work, but you might want to check in with BigKuba - he's the one with a degree in chemical engineering from MIT.

[dima]

35*0.12 = (35-x)*0.30 + x*0.05

solving for x you get 25.2ml of 5% solution and 9.8ml of 30% solution I think.

[jibij]

Holy crap. The potential answers are more confusing than the question. Trying to cipher out the nhtele/dima solution.

[Viva]

If I have a 30% solution and a 5% solution, how do I create 35ml of a 12% solution from them?

A 30% solution of what and a 5% solution of what to make 35 mls of a 12% solution of what?

[FigureEleven]

A 30% solution of what and a 5% solution of what to make 35 mls of a 12% solution of what?

Methamphetamines... its all the middle schoolers are cooking these days.

[jibij]

A 30% solution of what and a 5% solution of what to make 35 mls of a 12% solution of what?

acid solution

[eirikainersharp]

nhtele and spanky are both saying the same thing id differnt ways. nhtele's might be easier for a grade 8 to understand though.

finally 5 years of an honors math degree amounts to something!

[Viva]

acid solution

What acids? The same acid? Fuck! Dilute the 30% soln. to 12% and be done with it! Whats that? Hang on...14 ml of the 30% + 21 mls HOH. Is that right? Fuck, i used to do this shit in my head everyday. I think I;ll have another beer now.

[Viva]

Methamphetamines... its all the middle schoolers are cooking these days.

Well, thell them to stop it, god dammit! It's bad for their teeth.

[bossass]

Your kid must be smart. I'm pretty sure I wasn't doing shit like that in 8th grade.

[Dhelihiker]

Thats a tough one, cant help, I could assist in any joint rolling questions the lad might have.

[Mr.Scruff]

What age is 8th grade?

[The AD]

What acids? The same acid? Fuck! Dilute the 30% soln. to 12% and be done with it!

Just be sure to do it under a hood and wear gloves.

[AlpineMead921]

What age is 8th grade?

like 13ish

[The Suit]

nhtele is right
dima is right

Spanky's first equation should be 30x + 5y = 420

In long form, here's how to figure it out:

You are trying to get to 35 ml of 12% solution. That means when you're done mixing the the components you end up with 35 ml of liquid, and 4.2 ml (12% of 35 ml) of stuff dissolved in it.

If x is the volume of the 30% solution, and y is the volume of 5% solution, you know two things:

Total volume of the two solutions added together will be 35 ml. Therefore:

x + y = 35

Total volume of dissolved stuff will be 4.2 ml. The volume of dissolved stuff in the 30% solution is (0.30 * x), and the volume of dissolved stuff in the 5% solution is (0.05 * y). Therefore:

(0.30 * x) + (0.05 * y) = 4.2

From the first equation, we know that:

y = 35 - x

Substitute that into the second equation, and you get:

0.30 * x + 0.05 * (35 - x) = 4.2

0.30 * x + 0.05 * x - 0.05 * 35 = 4.2

0.25 * x - 1.75 = 4.2

0.25 * x = 2.45

x = 9.8

y = 25.2

[irul&ublo]

A 30% solution of what and a 5% solution of what to make 35 mls of a 12% solution of what?

Bacon...

[vinzclortho]

my cat's breath smells like catfood.

[GoldMember]

Only correction to The Suit (sorry, I'm nit-picky) is that Spanky's first equation should be: .30x + .05y = 4.20 (since we're dealing with percentages).

[The Suit]

Only correction to The Suit (sorry, I'm nit-picky) is that Spanky's first equation should be: .30x + .05y = 4.20 (since we're dealing with percentages).

They're the same. Just multiply both sides by 100. Since Spanky had started out with 30x + 5y, I went with it. You get the right answer either way.

[GoldMember]

Yeah, I know. I said I was being nit-picky! (Sorry, it's my nature....)

[Crass3000]

Its also alot easier to deal with whole numbers than percentages or decimals.