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

Question

Last September the sales total for a certain car dealership was 400% greater than the average monthly sales total for the other 11 months. The sales total for September was approximately what percent of the year´s sales?

A. 15 %
B. 27%
C. 31%
D. 42%
E. 75%

A. 15 %
B. 27% 
C. 31% 
D. 42% 
E. 75%

BrentGMATPrepNow · Accepted Answer

Let's assign some  nice values

Last September the sales total for a certain car dealership was 400% greater than the average monthly sales total for the other 11 months.  
Let's say that the AVERAGE monthly sales for the other 11 months =  $1 
400% of  $1  = $4
So, September's sales total =  $1  + $4 =  $5

So, the YEARLY total sales = (11)( $1 ) +  $5  =   $16

The sales total for September was approximately what percent of the year´s sales?  
 $5 /  $16   = 31.25%

Answer: C

arjtryarjtry · Answer

such problems are best done , by plugging

let every month sale or average sale per month (for 11 months) be 1 car / month.
so sale in september =  400% of monthly avg ... sorry 400% greater ( notice the difference) this is where we make mistakes. 
= (400/100)+1 = 5 times avg monthly sale
so sep sale/ total yr sale= 5/16 = (3 and something) %. from the ans , only C matches.

GMAT TIGER · Answer

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

x2suresh · Answer

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

Augustus · Answer

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?

asterixmatrix · Answer

andershv

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

KapTeacherEli · Answer

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.

superhix · Answer

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.

ScottTargetTestPrep · Answer

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

Fdambro294 · Answer

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%

bumpbot · Answer

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

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

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