Arithmetic with numbers

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Arithmetic with numbers

by danjuma » Sat Oct 02, 2010 9:23 pm
For each month of next year, company R's monthly revenue target is x dollars greater than its revenue target for the preceeding month. What is company R's revenue target for march of next year?

1. Company R's revenue target for december of next year is $310000

2.Company R's revenue target for september of next year is $30000 greater than its revenue target for June of next year
Source: — Data Sufficiency |

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by Geva@EconomistGMAT » Sun Oct 03, 2010 1:36 am
Answer seems to be a straightforward C.

Before rushing to the statements, examine the question stem, and see what pieces of the puzzle you need to answer the question. The question describes an arithmetic series: Each month is x more than the previous month.
For example, if January 2010 plan is 10,000, and x=1,000, then
feb 2010 = 10000+1000 =11000 (previous month +x)
mar 2010 = 11000+1000 = 12000 (previous month + same x)
etc.
Note that it is possible to find the plans for earlier months as well: If i know that oct 2010 is 20000 and x=1000, it is then possible to find previous months by subtracting x:
sep = 20000-1000 = 19000
aug = sep-1000 = 18000
etc.

Thus, in order to find any month next year, you need:
the value of x
the target for a single month (doesn't really matter which) to act as a baseline.

Stat. (1) provides the baseline (december), but not x
Stat. (2) basically tells you that 3x=30,000 (or x=10000), since September is "three jumps of x" more than june:
july is june +x
august = july +x = (june+x)+x = june+2x
sep = aug+x = (june+2x)+x = june+3x.
Thus, both statements are needed to answer the question: mar = dec-9x = 310000-9*10000.

where was your difficulty here? Did you read x taken as a percent, rather than a straightforward addition? Or is the OA something else, and I'm missing something crucial?
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