In a retail store, the average (arithmetic mean) sale for month M was

Hi, that is not the reason. The question isn't talking about average daily sales, but about average sale amount. For example, there can be more than 1 sale per day, it could be that they had 100 sales in Month M and 1 sale in month J or vice versa. So the number of days per month is not the reason for answer E, its the number of sales that we need to know.

Hi Mechmeera,

Since the prompt focuses on the average SALE per month, we need to know the TOTAL revenue and the TOTAL number of sales (re: the total number of 'transactions'). The number of days in the month has NO impact on this question.

You'll notice that the nothing in the prompt ever describes the total number of transactions in either month M or month J, so there is no way to determine the average sale for either month (nor how those averages relate to one another).

Final Answer:

GMAT assassins aren't born, they're made,
Rich

You are right. With the mean and no of days, you can count total sales.

Total sales = mean * no of days

However, in both cases, we have only total sales given. There's no way to find mean without no of days. So, both are together insufficient. Hence (E)

I highlighted the portion that I do not agree with.

Total sales = average sale * number of sales, not number of days.

Question is asking for comparison between Average Sale of Month M and Month J.
Average sale = \(\frac{Total Revenue from All Sales}{No. of Sales}\)
Neither of the options gives the No. of sales, so Answer is E.

Hi rakaisraka,

Since the prompt focuses on the average SALE per month, we need to know the TOTAL revenue and the TOTAL number of sales (re: the total number of 'transactions'). The number of days in the month has NO impact on this question.

You'll notice that the nothing in the prompt ever describes the total number of transactions in either month M or month J, so there is no way to determine the average sale for either month (nor how those averages relate to one another).

Final Answer:

GMAT assassins aren't born, they're made,
Rich

Average sale = total revenue/total no of sales.

Question asks about the average sale and the a) and b) gives the total revenue.

Since the denominator value is not given, we cannot calculate the average sale.

Hence E.

Solution:
Question is asking for the comparison between Average Sale of Month M and Month J.
Here the trap point is taking total sales as Total sales = mean * no of days
But the Average sale is given by \(\frac{(Total Revenue from All sales)}{(No of sales)}\)
To determine the average sale we need to know total revenue and number of sales.

Analysis of Statement 1: For month M, total revenue from sales was $3,500.
Here we know only about total revenue but no information about the number of sales.
Therefore the statement 1 is not sufficient. We can eliminate options A and D.

Analysis of Statement 2: For month J, total revenue from sales was $6,000.
Here also we know only about total revenue but no information about the number of sales.
Therefore the statement 2 is not sufficient.

Combining the statements 1 & 2; we get:
From statement 1: We know total revenue from sales was $3,500 for Month M.
From Statement 2: We know total revenue from sales was $6,000 for Month J
Still, we do not the number of sales, so we cannot answer the question.

So, the correct answer option is “E”.

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