Question 1203593
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"obtuse" means the measure of an angle is greater than 90 degrees.  For a polygon to have all angles obtuse, the average of the angle measures must be greater than 90 degrees.<br>
For a triangle, the average angle measure is 180/3 = 60 degrees.<br>
For any quadrilateral, the average angle measure is 360/4 = 90 degrees.<br>
For any polygon with more than 4 sides, the average angle measure is greater than 90 degrees.<br>
Of the answer choices, the hexagon is the only one with more than 4 sides.<br>
ANSWER: hexagon<br>
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The same solution, using formal algebra....<br>
The sum of the measures of the angles of a polygon with n sides is {{{180(n-2)}}}.<br>
The average measure of an angle of a polygon with n sides is {{{(180(n-2))/n}}}.<br>
We need the average measure of the angles to be greater than 90 degrees:<br>
{{{(180(n-2))/n>90}}}
{{{180n-360>90n}}}
{{{90n>360}}}
{{{n>4}}}<br>
For a polygon to have all obtuse angles, the number of sides of the polygon must be greater than 4.<br>