SOLUTION: A class containing a number P students has a test average of 70%. Another class containing a number N students has a test average of 92%. When the classes are combined, the new ave

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Question 310870: A class containing a number P students has a test average of 70%. Another class containing a number N students has a test average of 92%. When the classes are combined, the new average is 86%. What is the value of P/N?
It's the only problem in my homework assignment I can't solve. I think it should be set up as:
[(P X .70) + (N X .92)]/P + N equals .86
But how do I solve for P or N?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Don't solve for them, solve for P/N.
(x1+x2+x3+...+xp)/P=70
(y1+y2+y3+...+yn)/N=92
(x1+x2+...+xn+y1+y2+...yp)/(P+N)=86
.
.
.
(x1+x2+x3+...+xp)=70P
(y1+y2+y3+...+yn)=92N
(x1+x2+...+xn+y1+y2+...yp)=86%28P%2BN%29
+70P%2B92N=86P%2B86N+
+-16P=-6N
+P%2FN=6%2F16=3%2F8