Grid In from 10 Real SATS

<p>Its a grid in:</p>

<p>The average of the test scores of a class of P students is 70, and the average of the test scores of a class of N students is 92. When the scores of both classes are combined, the average score is 86. What is the value of P/N?</p>

<p>If someone could show me step by step how to do this i would really appreciate it. Thanks. btw the answer is 3/8</p>

<p>average = sum / number
So for the class of p students:</p>

<p>(equation 1) 70 = t1 / p where t1 is the sum of the grades for that class</p>

<p>For the class of n students:</p>

<p>(equation 2) 92 = t2 / n where t2 is the sum of the grades for this class.</p>

<p>Now, for the overall average of 86, we can apply the same definition of average and get the following.</p>

<p>avg = sum / number of values
(equation 3) 86 = t1 + t2 / (p+n)</p>

<p>From equations one and two, we get:
t1 = 70p and t2 = 92n</p>

<p>Substitute this into equation 3:
70p + 92n / (p+n) = 86
6n = 16p</p>

<p>Pick a value for either value, say, n = 16. If n = 16, then p = 6. So, p/n = 6/16</p>

<p>^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Mr Sanguine</p>

<p><a href="http://www.collegeconfidential.com/cgi-bin/discus/show.cgi?69/93597%5B/url%5D"&gt;http://www.collegeconfidential.com/cgi-bin/discus/show.cgi?69/93597&lt;/a&gt;&lt;/p>

<p>Thank you sooooooooo much!</p>