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Solution A is 20% acid.

Solution B is 50% acid.

How much of solution A and B do you need to mix together to come up with 90 mL of solution that is 40% acid?

Anyone? Please explain your work, too. Thanks!

L

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Joined

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19,280 Posts

Solution A is 20% acid.

Solution B is 50% acid.

How much of solution A and B do you need to mix together to come up with 90 mL of solution that is 40% acid?

Anyone? Please explain your work, too. Thanks!

L

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67,316 Posts

Joined

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Okay we know that A + B = 90 mLLeslie said:

Solution A is 20% acid.

Solution B is 50% acid.

How much of solution A and B do you need to mix together to come up with 90 mL of solution that is 40% acid?

Anyone? Please explain your work, too. Thanks!

L

So B = 90 - A

Now we also know that A times the .2 solution plus B times the .5 solution needs to yield 90 mL of the .4 solution -- so

A(.2) + B(.5) = 90 (.4)

And if we substitute from above this becomes

A(.2) + (90-A)(.5) = 90(.4)

Multiplying everything out

.2A + 45 - .5A = 36

Simplifying

45 - .3A = 36

Solve for A

45-36=.3A

9=.3A

30=A

If A = 30 then B=90-A or B=90-30 or B=60

So you need 30 mL of 20% acid plus 60 mL of 50% acid to yield 90 mL of 40% acid

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We basically had everything except we forgot the very first step you listed:

and so we kept getting stumped because we had two variables (x, y) and couldn't figure out the equation!So B = 90 - A

THANK YOU AGAIN...my son can leave for camp a happy man and I can explain the problem to my daughter when she gets home.

L

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10,391 Posts

Code:

```
<?php
$found = false;
for($x=0, $y=90; $x <= 90; $x+=1, $y-=1)
{
if(0.2 * $x + 0.5 * $y == 0.4 * 90)
{
$found = true;
echo "Use {$x}mL of 20% solution and {$y}mL of 50% solution.";
break;
}
}
if(!$found)
{
echo "Solution not found: maybe it's not an integral amount?";
}
```

Use 30mL of 20% solution and 60mL of 50% solution.

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NOPE Math is EASY -- WRITING is Hard!Thumper said:Math is hard.

Guess its all in how we're wired huh? Thump!

Your write very good stories but think math is hard.

I think math is easy but couldn't write a decent story to save my soul.

Thank God for Diversity. Be a boring world otherwise!

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Math AND writing are hard! I wish I could be good at something.

Melissa

Melissa

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