Need help helping my daughter with math

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Need help helping my daughter with math

Lynn Pettis

SSC Guru

Points: 442467
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November 12, 2010 at 5:24 pm

#63709

I know how to do this, but I am having a brain fart.
Her problem is this:
John wants to make a 10 fl oz 3% acid solution by mixing together a 10% acid solution and pure water.
I know I need two equations to solve this, but I am stuck. Once I have that, I know we can solve the problem.
Please, any guidance on how to create the 2 equations would be great.
I'm not asking for the equations, just help in figuring out what they are, hints, suggestions is all am asking for here. This way once I have it figured out, I can do the same with her.
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mister.magoo SSC-Forever Points: 47174 More actions · Answer 1

10% = *---------

3% = *-------------------------------

how many more "-" do you need to make 10% into 3%

and how much is a "-" worth...

I think...

MM

select geometry::STGeomFromWKB(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

Evil Kraig F SSC Guru Points: 100851 More actions · Answer 2

Lynn Pettis (11/12/2010)
John wants to make a 10 fl oz 3% acid solution by mixing together a 10% acid solution and pure water.

10% acid is 10% of the acid suspended in 90% of water. So 10 fl oz of acid is 1 oz of acid already diluted in 9 oz of water.

Figure out how much water to add to it to make it a 3% dilution, then cut back the amount of both by the ratio to reach 10 fl oz.

- Craig Farrell

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Lynn Pettis SSC Guru Points: 442467 More actions · Answer 3

mister.magoo (11/12/2010)
10% = *---------
3% = *-------------------------------
how many more "-" do you need to make 10% into 3%
and how much is a "-" worth...
I think...

Craig Farrell (11/12/2010)
Lynn Pettis (11/12/2010)
John wants to make a 10 fl oz 3% acid solution by mixing together a 10% acid solution and pure water.
10% acid is 10% of the acid suspended in 90% of water. So 10 fl oz of acid is 1 oz of acid already diluted in 9 oz of water.
Figure out how much water to add to it to make it a 3% dilution, then cut back the amount of both by the ratio to reach 10 fl oz.

You're both dancing around the problem like I am. I think I have intuitively solved the problem, but I may be wrong.

3 oz 10% acid solution + 7 oz pure water. (My daughter did say the numbers would "prettiful", menaing whole numbers.)

Now, to figure out if I am correct, and if so, go backwards to the two equations.

Still, any help or guidance would be welcome.

Lynn Pettis SSC Guru Points: 442467 More actions · Answer 4

Lynn Pettis

SSC Guru

Points: 442467

November 12, 2010 at 5:48 pm

#1250304

Okay, I think I'm wrong, back to the drawing board.

Lynn Pettis SSC Guru Points: 442467 More actions · Answer 5

Lynn Pettis (11/12/2010)
Okay, I think I'm wrong, back to the drawing board.

Actually, I think I'm right. Just can't seem to reverse engineer this properly.

mister.magoo SSC-Forever Points: 47174 More actions · Answer 6

Lynn Pettis (11/12/2010)
You're both dancing around the problem like I am....

You did ask for pointers, not the answer. If you want the answer, just say

MM

select geometry::STGeomFromWKB(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

Michael Valentine Jones SSC Guru Points: 64818 More actions · Answer 7

10 oz of a 10% acid solution has 1 oz of acid in it ( 10 *.10 = 1 )

10 oz of a 3% acid solution has .3 oz of acid in it ( 10 *.03 = .3 )

To get the .3 oz of acid you need for the 3% solution, you need the acid in 3 oz of a 10% acid solution ( 3 * .10 = .3 ) plus 7 oz of water.

Lynn Pettis SSC Guru Points: 442467 More actions · Answer 8

mister.magoo (11/12/2010)
Lynn Pettis (11/12/2010)
You're both dancing around the problem like I am....
You did ask for pointers, not the answer. If you want the answer, just say

Yes, yes I did. Unfortunately you gave me where I already was instead of a push to where I needed to go. Does that make sense?? :unsure:

Michael Valentine Jones (11/12/2010)
10 oz of a 10% acid solution has 1 oz of acid in it ( 10 *.10 = 1 )
10 oz of a 3% acid solution has .3 oz of acid in it ( 10 *.03 = .3 )
To get the .3 oz of acid you need for the 3% solution, you need the acid in 3 oz of a 10% acid solution ( 3 * .10 = .3 ) plus 7 oz of water.

Michael, thanks, you have helped me figure out how to present this to my daughter to see if she can figure this one out, and you helped me figure out that I was intuitively correct.

mister.magoo SSC-Forever Points: 47174 More actions · Answer 9

Absolutely - just didn't want to spoil the fun!

MM

select geometry::STGeomFromWKB(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

ps. One Orange Chip Points: 29423 More actions · Answer 10

i dont know if this would help but when i was a kid, i had a book that had hundreds of sets of simple mathematical quesions(simple ones). contained only +,-,*,/(more than 1 pair of these operations per question) but there was a time limit to solve them. Initially i used to take some time but after some practise i used to solve all of them in nearly half the given time. i didnt take help of paper to solve the questions but in mind. may be something like that would help her in improving her calculation time drastically.

2nd was solving similar type of questions from many sets (like the one you gave) and slowly i didnt need to use paper mostly. i just used to arrive at a final formula to solve the problem, used to note that down on paper and solved it.

giving her many problems (similar type) will help her in solving them much faster... may be you can buy books from different publications for same grade to get more questions.

Practise is the key

Pradeep Singh

kevlray SSCommitted Points: 1908 More actions · Answer 11

Half the time when I help my one daughter with Algerbra, she crys (out of frustration). What seems so simple and clear to me, confuses her.

kgottfredsen Mr or Mrs. 500 Points: 542 More actions · Answer 12

how much acid required in final 3% mixture: 10oz * .03 = .3oz of acid

how much of 10% mixture will it take to make .3oz of acid: x * .10 = .3 -or- x = .3/.10

so 3oz of 10% acid solution + 7oz of water

Richard Warr SSCertifiable Points: 6968 More actions · Answer 13

Alternatively, Bananas contain 0.3% acid (they really do) and would provide John with a tasty alternative to his problem.

Need help helping my daughter with math

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