Help with math problems!

<p>I need help with a few math problems that are in my SAT packet.
I just want to how to solve these problems mathematically, besides guess and check.
Thank you very much.</p>

<ol>
<li>If 60 percent of x is equal to y percent of 40, where y > 0, what is the value of x/y</li>
</ol>

<p>A) 2/3
B) 3/4
C) 4/3
D) 3/2
E) 5/3</p>

<ol>
<li>Forty percent of the songs played on a certain mp3 player are 4 minutes long, thirty-five percent of the songs are 3 minutes long, and twenty-five percent of the songs are 2 minutes long. What is the average (arithmetic mean) number of minutes per song played on this mp3 player?</li>
</ol>

<p>A) 3.00
B) 3.05
C) 3.10
D) 3.15
E) 3.20</p>

<ol>
<li>The number of registered voters in City X increased by 18% over last year. There are now 12,803 registered voters. How many registered voters were there last year?</li>
</ol>

<p>A) 10,498
B) 10,850
C) 11,302
D) 14,513
E) 15,613</p>

<p>1) 0.6x=0.4y</p>

<p>x/y = 0.4/0.6 = 2/3</p>

<p>2) can't do this one</p>

<p>3) 1.18x=12803</p>

<p>x= 10850</p>

<p>Ha, I'll just answer question 2)</p>

<p>average number of minutes per song = (40<em>4+35</em>3+25*2)/100= 3.15 min</p>

<p>Answer is D
:)</p>

<p>lol I did the same thing and got 3.35.</p>

<p>lol you could always use a calculator</p>

<p>The</a> Official SAT Question of the Day</p>

<p>Why is the SAT official question of the day's answer is D? I got it right, but I want to know why.</p>

<p>
[quote]
Why is the SAT official question of the day's answer is D? I got it right, but I want to know why. [/quote</p>

<p>The price of the half gallon of milk is x, and the price of the gallon of milk is y. Because we need two half gallons to find the price difference, we then use 2x.</p>

<p>Since the question is asking the difference is price between the two milks, z, we set the equation:</p>

<p>2x-y=z</p>

<p>Because all the answer choices are equal to 0, just subtract z from each side:</p>

<p>2x-y-z=0</p>

<p>(The price of two half gallons minus the price of one full gallon minus the price difference between the two equals zero)</p>

<p>2x - z = 1
2x - y - z = 0</p>

<p>[D]</p>