From 1
Sn=3124..but no relation between the terms of the series..not sufficient
From 2
Sn=4n..but Sn is not provided...not sufficient
Combining
3124=4n
or 781=n...sufficient
Ans option C
sequence
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Source: Beat The GMAT — Data Sufficiency |
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Patrick_GMATFix
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This question is easier than it seems. The little subscript numbers are indexes. They indicate the position of the number in a sequence. t1 is the first number and t3 is the 3rd number in the sequence. Because the sequence ends with tn, asking for the value of n is the same as asking for the number of terms in the sequence.
Rephrase: How many terms are in the sequence.
You have to look at the statements together since they give you 2 of the 3 parts of the average equation: avg = (Sum of terms)/(# of terms). (1) gives you the sum and (2) gives you the avg. You can solve for the # of terms. The answer is C.
To better understand, have a look at the video solution. This is GMATPrep question 1035
-Patrick
Rephrase: How many terms are in the sequence.
You have to look at the statements together since they give you 2 of the 3 parts of the average equation: avg = (Sum of terms)/(# of terms). (1) gives you the sum and (2) gives you the avg. You can solve for the # of terms. The answer is C.
To better understand, have a look at the video solution. This is GMATPrep question 1035
-Patrick
