Please, explain the answer of question 30A (below). The OE of the OG is not good at all. In summary, they say this:
"Both ABC and XYZ sales were at or above the citywide average for every single month in 2010. Thus their combined sales must have been greater than the combined sales of the two dealers not included in the graph. Therefore ABC Cars and XYZ Automotive must have accounted for more than half of all used-car sales in City Z in 2010."
Please, provide a more detailed explanation.Also, what would have happened if the total number of dealers (not only in the graph) had been 20? The answer would have not been the same, right? That's why I believe that the OE is not sufficient to explain the answer. Please your help.
Actually, the OE is fine.
Take a simpler view:
Average of 4 numbers is 15. (Total sum of all four numbers will be 60.)
Two of the numbers are 20 and 22. Both the numbers are more than the average.
What can you say about the other two numbers? Can you say that they together will account for less than half of total sum? Yes, you can. Since the contribution of the given two numbers is more than half of the total sum, the contribution of the other two numbers will be less than half of the total sum.
Similarly, in this question you have 4 car dealers (given in the question). The total number of car dealers cannot be 20 since you are given that the total number is 4.
Two of them account for more than half of the total sales almost every month (since they lie either above or at average). Hence, for 2010, the two of them will account for more than half of all sales.
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