Last September the sales total for a certain car dealership was 400%

11 moth avg = x
11 month total = 11x
sept = 400% of x + x = 5x
sept/totoal = =5x/(11x+5x) = =31%

5x/11x+5x = 5/16 = 31%

Hi guys, I just did the following question:

Last September the sales total for at certain car dealership was 400% greater than the average (arithmetic mean) monthly sales total for the other 11 months of the year. The sales total for September was approximately what percent of the years sales?

1. 15%
2. 27%
3. 31%
4. 42%
5. 75%

My way of solving this is normalizing the average monthly sales on the other 11 months to =1. Thus the sales in September is 4 (400%*1) and therefore September made out: 4/(4+11)=4/15 of the years sales according to my logic.

Yet the OA suggests the same way of solving the question except that it claims that the sales in September is 1 + (400%*1) = 5, such that the fraction is 5/16 which is approximately 31%.

Would you tend to agree that this is an error in the software or am I completely missing something?

andershv

the question says 400% greater than avg of remaining 11 months so the OA explanation is correct

Pay particular attention to asterixmatrix's point; the testmakers know that this is an easy trap to fall for, and will frequently include the trap as a wrong answer choice. % increase + 100% = % of total; since we are going up by 400%, we are therefore ending with a result of 500%, which we plug into our equation.

Last September the sales total for at certain car dealership was 400% greater than the average (arithmetic mean) monthly sales total for the other 11 months of the year. The sales total for September was approximately what percent of the years sales?

The question can be easily solved by assuming that the dealership sold 100 cars each month.

If the dealership managed to sell 400% more cars in September than in all other months, it means that the sales total for September was 100+400% or 500 cars. At the same time, the sales total for the other 11 months equals 11*100 or 1100 cars. 1100+500 equals 1600 cars sold throughout the year.

The number should then be divided by 500 cars sold in September in order to get percent of the year sales 1600/500≈32%, hence the correct answer is C.

We can let the average monthly sales = 1 and thus the sales in September were 5.

Thus, September is 5/(5 + 11) = 5/16 = 0.3125 which is approximately 31%

Answer: C

Let A = Monthly Average $Sales for the other 11 months

thus, the Total $Sales over the last 11 months = 11 * A


"September's Sales were 400% greater" than the Average $Sales over the other 11 months

400% Greater -----> (400 + 100)% * A = 5 * A


September Sales = 5A
Total Sales over other 11 months = 11A
______________________________________
Total YEAR Sales = 16A


"September's Sales is approx. what percent of the year's Total Sales?"

[ (5A) / (11A + 5A) ] * 100% =

(5/16) * 100% =


Estimating the Percentage, 5/16 is a Little Less than < 1/3 -----> which is 33.33%

Thus, the Percentage% Answer Choice should be a Little Less Than < 33.33%


-C- 31%

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