Bunuel
Fresh GMAT Club Tests' Challenge Question:
Does regular polygon X have more than 6 sides?
(1) The ratio of the length of the longest line that can be drawn between two vertices of polygon X to the length of any one side of polygon X is greater than 2.
(2) The degree measure of an interior angle of polygon X is NOT an integer.
M36-139
Official Solution:Does regular polygon X have more than 6 sides? (1) The ratio of the length of the longest line that can be drawn between two vertices of polygon X to the length of any one side of polygon X is greater than 2.
Consider regular polygons below:
Notice that when we increase the number of sides, the ratio of the longest diagonal to the side increases. So, more sides the larger the ratio.
Let's check what this ratio is for a 6-sided regular polygon, hexagon:
The degree measure of \(\angle AOB = \frac{360°}{6}=60°\). Since AO = BO, then \(\angle ABO = \angle BAO = \frac{180° - 60°}{2}=60°\). So, triangle ABO is equilateral. Thus, AB = AO, but AO is half the diagonal, so \(diagonal:side=2:1\)
Since we are given that the ratio for our polygon is more than 2 and we know that the ratio increases as we increase the number of sides, then our polygon must have more than 6 sides. Sufficient.
(2) The degree measure of an interior angle of polygon X is NOT an integer.
The degree measure of an interior angle in a regular polygon is \(\frac{(n-2)*180°}{n}\), where \(n\) is the number of sides.
So, we are told that \(\frac{(n-2)*180°}{n}\neq integer\). Notice that since 180 is divisible by 3, 4, 5, and 6, then for these values of \(n\), \(\frac{(n-2)*180°}{n}\) will be an integer. Thus, the number of sides, \(n\), must be more than 6. Sufficient.
Answer: D