<p>Whats the best approach for this question, and a good formula for arthimetic questions in general</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>Not 100% sure but this is how i would do it.
70P+92N=(P+N)86
70P+92N=86P+86N
70P+6N=86P
6N=16P
P/N=6/16</p>
<p>Easy to do if you think it out...it's just weighted average. </p>
<p>70P + 92Q / P + Q = 86</p>
<p>70P + 92Q = 86P + 86Q</p>
<p>Then, from here, just solve for P/Q, which I think turns out to be 3/8.</p>
<p>Just a weighted average, but if you have never done a weighted average then it could be a difficult question.</p>
<p>Yes, weighted average is new to me;can someone please explain?</p>
<p>For weighted average, every factor essentially has its own "weight" or factor of contribution...basically, how much a particular value contributes to the average.</p>
<p>Say you have 6 tests...on five of them you got a 95% and on one of them you got a 100. To average this, you'd "weight" them with the number of tests being the weight factor. Example:</p>
<p>5(95) + 1(100)/6 = average </p>
<p>Gahh, I'm not much of a teacher...</p>