DSQ: Calculating the height of an acute / obtuse triangle - GMAT Quantitative

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Question

Two sides of a triangle are 6 and 6. What is the height of the triangle?

(1) The third side of the triangle is also 6.

(2) One of the angles of the triangle is .

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Answer

Statement (1) informs us that the triangle is an equilateral triangle, with all sides equal to 6. Therefore, the height would divide the triangle into two 30-60-90 triangles, which have side lengths in a ratio of . For this triangle the hypotenuse would be 6 and the base would be 3. The height would therefore be . SUFFICIENT

Statement (2) also lets you deduce that the triangle is an equilateral triangle. Since the triangle is either isoscles or equilateral (at least 2 sides are equal), that means that two angles are equal. Therefore, if one angle is , the other two also must be . See above. SUFFICIENT

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