Hi All,

The GMAT is based heavily on patterns; your ability to recognize (or discover) patterns will help you to speed up and score at a higher level on Test Day. In "sequence" questions, at least one pattern will exist (the sequence has to based on a pattern; it's called a "sequence" because there's some "rule" that governs the sequence). In a prompt such as this, if you don't immediately see the pattern, then you can figure it out with a bit of experimentation.

Here, we're told to take the SUM of the positive ODD integers from 1 to N..... There's a pattern to this sequence; let's figure out what it is....

If N = 3

2 terms

1 + 3 = 4

If N = 5

3 terms

1 + 3 + 5 = 9

If N = 7

4 terms

1 + 3 + 5 + 7 = 16

Look at the sums. Do you recognize a pattern?

4....9......16......they're all PERFECT SQUARES!!!!

The next part of the question tells us the SUM of the terms in this sequence = 169 which is ALSO a perfect square (it's 13^2), so we can use this deduction along with the existing pattern we discovered to figure out the answer to the question.

169 = 13^2 = 13 terms

So we need the first 13 positive ODD integers starting with 1. We can physically list them out, if necessary...

1 3 5 7 9

11 13 15 17 19

21 23 25

Final Answer:

GMAT assassins aren't born, they're made,

Rich

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# Rich Cohen

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