There are x numbers in list L, where x is a positive integer, and there are y numbers in list M, where y is a positive integer. The average (arithmetic mean) of the numbers in list L is p, and the average of all the numbers in both lists L and M is q. Which of the following expressions is the average of the numbers in list M?
Options:
A) (qy - px) / x B) (qy - px) / y C) (p + q)x / y D) [(q - p)x - py] / (x + y) E) [(q - p)x + qy] / y
You can eliminate Answer A (it divides by 2)   Answer B: (QY-PX)/Y = (7.8 - 4)/3 = 3.8/3 This is clearly too small. Eliminate B.   Answer C: (P+Q)X/Y = (4.6)(2)/3 = 9.2/3 This is too big. Eliminate C.   Answer E is all that's left, but I'll check it just to be sure....   Answer E: [(Q-P)X +QY]/Y = [(0.6)(2) +7.8]/3 = 9/3= 
<gadget id="calculator">9/3</gadget>
<output>3</output>
3. This is a MATCH.   Final Answer:[(q - p)x + qy] / y
<result>E</result>
There are x numbers in list L, where x is a positive integer, and there are y numbers in list M, where y is a positive integer. The average (arithmetic mean) of the numbers in list L is p, and the average of all the numbers in both lists L and M is q. Which of the following expressions is the average of the numbers in list M?