<ol>
<li>Solution X is 10 percent alcohol by volume, and solution Y is 30 percent alcohol by volume. How many milliliters of solution Y must be added to 200 milliliters of solution X to create a solution that is 25 percent alcohol by volume?</li>
</ol>
<p>250/3
500/3
400
480
600 </p>
<p>(600)</p>
<p>{0.3y+200*(0.1)} / (y+200) = 1/4
so y=600
Let me know if you have any questions about the equation above</p>
<p>i didn’t get it srry :/</p>
<p>I got no idea how to solve it using a specific formula, but here is how I would solve this question: For every answer check how many milliliters of alcohol does the solution have, then add it to the 20 grams ( 200 x 10% ) of solution X.</p>
<p>1) 250/3 = 83.3333
250/3 x 0.3 = 25
25+20=45
45/83.3333+200= 0.16x 100= 16%</p>
<p>2) 500/3 = 166.66667
166.6667 x 0.3 = 50
50+25=75
75/166.6667+200= 0.2x100 = 20% </p>
<p>keep checking every answer, until you get the right one:</p>
<p>5) 600x 0.3= 180
180+20=200
200/800= .25x100= 25%</p>
<p>suppose you need to add A milliliters of solution Y to the overall solution.
Then the alcohol amount of solution Y is A* 30% = 0.3A
Likewise, the alcohol amount of 200 milliliters of solution X is 200* 10%=20
So you have the total amount of alcohol 0.3A+20, whereas the total amount of the overall solution is A+200
According to the question, the solution is 25 percent alcohol by volume, so you have the equation, </p>
<p>totally alcohol divide total amount of solution equals 25%</p>
<p>so (0.3A+20) / (A+200) = 25%</p>
<p>So A = 600.</p>
<p>the easy way, and the best way for those that don’t like using formulas is to go through and use the answers to find the answer.</p>
<p>From the problem, you can find out that 20ml out of the 200 ml solution x is alcohol. Then you can do the same for all the answers. For Answer A: 25 ml of the 83.3 ml is alcohol. Then you just add both totals: 45 ml out of 283.3 total ml is alcohol, which is 15.8 percent. Therefore, Answer A is not correct. </p>
<p>You can go through all the answers like this, until finally you find out that the last answer gives you a 25 percent alcohol solution: 20ml alcohol in solution x + 180ml alcohol in solution y divided by 200ml total solution x + 600ml total solution y = 25%</p>
<p>Hope this helps. One of the best strategies for SAT math is to use the answers to your advantage. I got a 770 with that strategy (though it should’ve been 800, but it was scored wrong)</p>
<p>Good luck! Hope this helped.</p>