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题库 / Prep2007E1-DS-79
If the terms of a sequence are t1, t2, t3, . . . , tn, what is the value of n ?
(1) The sum of the n terms is 3,124.
(2) The average (arithmetic mean) of the n terms is 4.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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you should start this question the same way you start all questions involving averages: by using the 'magic formula'
average = sum / number of data points
or
(average)(number of data points) = sum
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