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The GMAT Math practice question is a problem solving question in geometry

What is the measure of the radius of the circle that circumscribes a triangle whose sides measure 9, 40 and 41?

1. 6
2. 4
3. 24.5
4. 20.5
5. 12.5

The correct choice is (D) and the correct answer is 20.5.

From the measure of the length of the sides of the triangle, 9, 40 and 41 we can infer that the triangle is a right angled triangled. 9-40-41 is a Pythagorean triplet.

In a right angled triangle, the radius of the circle that circumscribes the triangle is half the hypotenuse.

In the given triangle, the hypotenuse = 41.

Therefore, the radius of the circle that circumscribes the triangle = = 20.5 units.

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