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Variable in the stem

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by lightbulb » Mon Aug 04, 2008 6:00 pm
Suppose a DS 'value' question contains a variable X in the stem, and one of the statements is sufficient to give the answer as f(X). Would you say that the statement was sufficient to answer the question? Here is an example:

Jack can type at the rate of N words per minute. How many hours did it take Jack to finish typing the book?

(1) The book has 21600 words.

(2) If Jack typed any faster, he would finish the book before Jim

Now, (1) gives the answer as a function of N. Can we say (1) is sufficient? My thought is No. I am wondering what GMAC and GMAT instructor's think about this.
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Source: — Data Sufficiency |

by Ian Stewart » Tue Aug 05, 2008 3:24 am
When a question asks you for a value, you only have sufficient information when you can get a unique, numerical answer for the value. So if you find that, say,

x = 3 or 1

you do not have sufficient information; you must get only a single value for x. If you find that

x = 3N + 1

you also do not have sufficient information; you must get a numerical answer for x.
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by lightbulb » Tue Aug 05, 2008 7:55 pm
Appreciate your response, thanks.
Ian Stewart wrote:When a question asks you for a value, you only have sufficient information when you can get a unique, numerical answer for the value. So if you find that, say,

x = 3 or 1

you do not have sufficient information; you must get only a single value for x. If you find that

x = 3N + 1

you also do not have sufficient information; you must get a numerical answer for x.
Join the discussion