Multiple choice

The radius of the circle in which an isosceles triangle of sides 20 cm, 20 cm and 24 cm can be inscribed is

  1. 12 cm

  2. 15 cm

  3. 13 cm

  4. 12.5 cm

  5. 17 cm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For an isosceles triangle with sides 20, 20, 24, the height h to the base 24 is sqrt(20^2 - 12^2) = sqrt(400 - 144) = sqrt(256) = 16. Area = 0.5 * base * height = 0.5 * 24 * 16 = 192. Circumradius R = (abc) / (4 * Area) = (20 * 20 * 24) / (4 * 192) = 9600 / 768 = 12.5.

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