Homework Help.

[death2all110]

Okay, homework help, I'm not thinking clearly apparently,because I keep swearing up and down its wrong, so here goes....

"Marin Caswell needs 10% acid solution for a chemistry experiment. How much 5% acid should she mix with 60mL of 20% acid to get a 10% solution?"

I got 60.5mL of 5% acid.

But I think I might be wrong. Any input?

To prove I actually tried working it out and I'm not just trying to get you guys to solve something for me...

Obviously my handwriting sucks....

 

[Kelmar]

I could be mistaken...


but wouldn't the correct equation would be:

.05x + .2(60) = .1(x+60)

 

[Member243850]

Well done,

NEVER be afraid to ask for help!

Seriously well done it takes a man to do ask for help and yes I can see you are trying too so well done!

:-D

Hmmm okay that question is not very well worded but lets ignore that for the moment and give it a bash.

From what I can see, the total amount of acid is 60 ml right?

Or am I maybe wrong?

Lets go!



BODMAS

Brackets
Of
Division
Multiply
Addition
Subtraction

So you say this is how we do it right?

Lets say you are right with your current way of thinking

Here is the solution but you need to tell me how I got there is it a deal?

Spoiler

I am glad to see you are doing maths... most children for some strange reason are scared of doing it.

Well done!!

 

[Member243850]

Obviously my handwriting sucks....

LOL

xD

I have the WORST hand writing in the world!

So don't feel down about that mindless detail!

 

[Stuntman]

My chemistry may be a bit off here, but I think my math is right:

60mL of 20% solution is 12 mL of Acid and 48 mL of Water. (By Acid, I mean 100% acid)

Let Y be the total amount of the final mixture.

Y mL of 10% solution is Y/10 mL Acid and 9Y/10 mL Water.

Let X be the total amount of 5% solution.

X mL of 5% solution is X/20 mL Acid and 19X/20 mL Water.

You get these two linear equations:

12 mL Acid + X/20 mL Acid = Y/10 mL Acid

48 mL Acid + 19X/20 mL Acid = 9Y/10 mL Acid

Take out the mL Acid and you get

12 + X/20 = Y/10 => 120 + X/2 = Y
48 + 19X/20 = 9Y/10

By substituting Y with 120 + X/2 in the second equation, you are left with X only in one equation.

Solve and X = 120 mL.

 

[Member243850]

Hmm you see the question is worded very badly or is it just me?

I don't 200% understand what the question is asking for as it is very very ambiguous.

At least to me it is.

The question itself is a problem.

If 60 ml = 100%

Just for arguments sake.

So if 60 ml = 100%

then 10% = 6 milliliters

Am I correct here right guys?

so

if 6 = 10%

then surely

3 milliliters = 5%

???

You see the question is an issue here to me at least it is

 

[Kelmar]

I'm pretty sure they want to know how much (variable) 5% acid would need mixed with (fixed 60mL) 20% acid to make 10% acid.

 

[Member243850]

Hmmm I am not 100% sure.

I have got a slight feeling it is not worded right.

Hell I could be totally wrong though

 

[death2all110]

See that's why I'm getting stuck. Unfortunately my teacher is german, so german is her native language, and she has a strong accent. So her homework assignment is oddly worded and I've suffered through most of it. I think kelmar's 1st reply is right though, and my math is definitely off. Ill take another crack at it.. Thanks!

Took another crack at it. and got a vastly different answer! Looks to be the same as Stuntman's

X=120mL

Picture of my math, with *somewhat* better writing....

 

[Kelmar]

FWIW, that's the answer I got and it makes sense (to me) too

Working it backwards and plugging the solution into the equation makes sense when you do the math.

 

[death2all110]

Glad I came here, I would have looked stupid turning in my original answer! xD Especially when I can't re-create it! Funny how my ORIGINAL work was missing the X after 0.05 and thus drastically changing the answer. Going back to my original work, and replacing 0.05 with 0.05x and doing the equation that way yields the same answer.

 

[Kelmar]

Hopefully it's right!

Otherwise we'll all look stupid hiding behind our anonymous avatars.

 

[Stuntman]

See that's why I'm getting stuck. Unfortunately my teacher is german, so german is her native language, and she has a strong accent. So her homework assignment is oddly worded and I've suffered through most of it. I think kelmar's 1st reply is right though, and my math is definitely off. Ill take another crack at it.. Thanks!

Took another crack at it. and got a vastly different answer! Looks to be the same as Stuntman's

X=120mL

Picture of my math, with *somewhat* better writing....

In your table, the Solution 1 Acid entry should be 0.05X, not 0.5X.

 

[TJGoSurf]

Looks like everything is all solved here.

College algebra? Those days were fun. Just think you'll get to stare at this one day:

 

[Kelmar]

I remember those days! Too bad (or lucky me) I don't have to do stuff like that anymore.

 

[TJGoSurf]

I remember those days! Too bad (or lucky me) I don't have to do stuff like that anymore.

Math is the greatest thing ever. Those who do not know it are doomed to repeat it. Or was that history? Seems to work for both.

I met a friend at a bar. He teaches a basic math class at the community college. We were hammered and grading papers. Alcohol may inhibit the thinking process but I can't mess up questions like '5-8'.

 

[Kelmar]

Math is the greatest thing ever. Those who do not know it are doomed to repeat it. Or was that history? Seems to work for both.

I met a friend at a bar. He teaches a basic math class at the community college. We were hammered and grading papers. Alcohol may inhibit the thinking process but I can't mess up questions like '5-8'.

What I like about math is that there is ALWAYS right answer. You don't have to worry about which version of "there" to use or about punctuation. It's cut, dry and right or wrong!

 

[TJGoSurf]

I'll show you!

1=2
1*2=2*2 Multiply both sides by 2
2=4
2-3=4-3 Subtract 3 from both sides
-1=1
(-1)^2=1^2 Square both sides
1=1

As you can see 1=2.

 

[Kelmar]

Ah... those are and were the best

 

[TJGoSurf]

 

[Kelmar]

Hadn't seen that one!

 

[9to5cynic]

I was never really good at math, I was just okay, but it was always one of my favorite subjects because that's the thing: no matter what, there is a definitive answer. It's not like other subjects where answers are up to interpretations.

 

[TJGoSurf]

Quick!

Find the particular solution of

y′=5
given that when x=0,y=2.

 

[death2all110]

Thanks I'll be sure to fix that xD

And thanks to everyone else for the help!

 

[Stuntman]

I was never really good at math, I was just okay, but it was always one of my favorite subjects because that's the thing: no matter what, there is a definitive answer. It's not like other subjects where answers are up to interpretations.

I love math. I actually miss it as now that I'm out of school, I don't get very many opportunities to do much math. I jumped at the chance when I saw this thread.

There's not necessarily a definitive answer. There do exist unsolvable problems. Such problems are more primarily in the realm of Computer Science. In math, an unsolvable problem would be finding an equation for solving the zeros of a polynomial of degree 5 or higher. For polynomials of degree 2, you have the quadratic equation which is well known. There is no answer for a polynomial of degree 5 or higher.

Thanks I'll be sure to fix that xD

And thanks to everyone else for the help!

You're very welcome. I had a lot of fun using my high school algebra again.