Hi All,

This is a great 'concept' question that many Test Takers would probably get wrong (because they would refuse to do any work on the pad).

We're told that triangles ABC and CDE are EQUILATERAL (meaning that each has 3 equal sides). We're asked for the total PERIMETERS of the two triangles.

Fact 1: Line segment AE measures 25 meters.

At first glance, you might think that you don't know the exact side lengths of either triangle, so you won't be able to figure out the perimeters. Instead of assuming that this is insufficient data, take a moment to 'play around' with the information. Let's TEST VALUES and see what happens.

Since we're adding one side from each triangle and getting a total of 25 meters....

IF we have....

A side of 1 and a side of 24.

Total perimeter would be 3(1) + 3(24) = 3+72 = 75

A side of 2 and a side of 23.

Total perimeter would be 3(2) + 3(23) = 6+69 = 75

A side of 3 and a side of 22.

Total perimeter would be 3(3) + 3(22) = 9+66 = 75

The total perimeter is ALWAYS 75.

Fact 1 is SUFFICIENT

Fact 2: Side BC is 2/3 as long as side DE.

This Fact gives us no 'numbers' to work with, so there's no way to calculate either perimeter (much less the total perimeter).

Fact 2 is INSUFFICIENT

Final Answer:

The take-away from this question is that it doesn't take much effort to prove whether a pattern exists or not. Get in the habit of doing that little bit of extra work (especially when you 'think' that a Fact is insufficient) and you'll be better able to pick up all of the available DS points on Test Day.

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

Rich

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