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DS problem guidance

by roc101 » Sun May 25, 2014 3:12 pm
Two DS questions that I would appreciate some assistance in understanding. Thanks!

In a certain conference room each row of chairs has the same number of chairs, and the number of rows is 1 less than the number of chairs. how many chairs in a row?
1. There are a total of 72 chairs
2. After 1 chair is removed from the last row, there is a total of 17 chairs in the last 2 rows.


For each month of next year, Company R's monthly revenue target is x dollars greater than its monthly revenue for the preceding month. What is company R's revenue for March of next year?
1. Company R's revenue target for Dec is 310,000
2. Company R's revenue target for september of next year is $30,000 greater than its revenue target for June of next year.
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Source: — Data Sufficiency |
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by theCodeToGMAT » Sun May 25, 2014 9:39 pm
Please post one question per thread!

Thanks!
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by GMATGuruNY » Mon May 26, 2014 1:55 am
In a certain conference room each row of chairs has the same number of chairs, and the number of rows is 1 less than the number of chairs in a row. How many chairs are in a row?
1. There are a total of 72 chairs
2. After 1 chair is removed from the last row, there is a total of 17 chairs in the last 2 rows.
Statement 1: There is a total of 72 chairs.
(rows)(chairs per row) = 72.
Thus, the number of rows and the number of chairs per row must be a factor pair of 72:
1*72
2*36
4*18
6*12
8*9
Since the number of rows must be 1 less than the number of chairs per row, only the last factor pair works:
8 rows, 9 chairs per row, for a total of 72 chairs.
SUFFICIENT.

Statement 2: After 1 chair is removed from the last row, there is a total of 17 chairs in the last 2 rows.
Thus, before the 1 chair is removed, the number of chairs in the last two rows is 18, implying that there are 9 chairs per row.
SUFFICIENT.

The correct answer is D.
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by GMATGuruNY » Mon May 26, 2014 2:07 am
roc101 wrote: For each month of next year, Company R's monthly revenue target is x dollars greater than its monthly revenue for the preceding month. What is company R's revenue for March of next year?
1. Company R's revenue target for Dec is 310,000
2. Company R's revenue target for september of next year is $30,000 greater than its revenue target for June of next year.
Each month, the target increases by x dollars.

Statement 1:
From March to December = 9 months.
Thus:
December = March + 9x.
March = December - 9x.
Since December = 310,000, we get:
March = 310,000 - 9x.
No way to determine the value in March.
INSUFFICIENT.

Statement 2:
From June to September = 3 months.
Thus, the increase from June to September = 3x.
Since 3x = 30,000, x=10,000.
No way to determine the value in March.
INSUFFICIENT.

Statements combined:
Since x=10,000 and March = 310,000 - 9x, we get:
March = 310,000 - (9*10,000) = 220,000.
SUFFICIENT.

The correct answer is C.
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I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
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I unlock the best way for YOU to solve problems.

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