Percents

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Percents

by heshamelaziry » Sun Nov 29, 2009 3:00 pm
Last September the total sales for a certain car dealership was 400% greater than the average monthly sales total for the other 11 months of the year. The sales total for September was approximately what percent of the year's sales ?

15%

27%

31%

42%

75%

OA C
Last edited by heshamelaziry on Sun Nov 29, 2009 8:58 pm, edited 1 time in total.
Source: — Problem Solving |

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by thephoenix » Sun Nov 29, 2009 8:39 pm
imo c 31%

LET TOTAL SALE BE X FOR THE 11 MONTHS AVG SALES WILL BE X/11
SEPTEMBER SALES WILL BE 4X/11+X/11=5X/11

TOTAL YEARS SALES=X+5X/11=16X/11

sales total for September / YEARS SALES=(5X/11) /(16X/11)=APPROX 31%

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by Stuart@KaplanGMAT » Mon Nov 30, 2009 12:01 am
thephoenix wrote:imo c 31%

LET TOTAL SALE BE X FOR THE 11 MONTHS AVG SALES WILL BE X/11
SEPTEMBER SALES WILL BE 4X/11+X/11=5X/11

TOTAL YEARS SALES=X+5X/11=16X/11

sales total for September / YEARS SALES=(5X/11) /(16X/11)=APPROX 31%
Good solution, but we could have simplified things a bit by ignoring the averages.

Just let every other month have sales of X and September have sales of 5X (as you did).

Then we simply take Sept/Year = 5X/(5X+11X) * 100% = 5/16 * 100% = (500/16)% which is a bit more than 30%.
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by Gmatter2.0 » Mon Nov 30, 2009 7:33 pm
VIC

Let the Sales per month for 11 months other than september be equal, and let the sale be 1000.
Sept Sales=400/100 *1000+1000=5000

Total Sales =11000+5000
=16000
Now 5000=x% * 16000

x=5/16 *100=31.25% ~= 31%

Answer is C.