Sally states that a triangle can only have one obtuse or right angle. However, a triangle must have at least two acute angles. Is Sally correct? Explain.

Answer:

Sally is correct. The sum of the interior angle measures of a triangle must equal 180 degrees. If a triangle had two right angles (90 + 90 = 180) or two obtuse angles (both greater than 90), the sum of just those two angles would be 180 degrees or more, leaving no room for a third angle. Therefore, a triangle can only have at most one right or obtuse angle, and the other two angles must be acute.