Hi All,

This question has some great Number Property shortcuts built into it (which you can take advantage of to save some time and avoid some of the math "work").

We're given the set {1, 6, 11, 16, 21}. We're asked which set of additional numbers, when added into this set, will NOT change the set’s mean.

In the original set of numbers, notice how the 5 terms are 'evenly spaced'; this means that the average MUST be the 'middle term' --> the average is 11.

Looking at the three options, notice how each has 3 terms. To add 3 terms to the given set and NOT change the average, we need the average of the 3 terms to be 11. By extension, we need the SUM to = 33.

A quick estimate of Roman Numerals 1 and 2 proves that neither has a sum of 33 (the sums are both TOO SMALL). Eliminate Answers A, B and D.

Adding up the terms in Roman Numeral 3 gives us a sum of 33, so this set 'fits' what we're looking for.

Final Answer:

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

Rich

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Rich Cohen

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http://www.empowergmat.com

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