Multiple choice general knowledge math & puzzles

What is the radius of the incircle of the triangle whose sides measure 5, 12 and 13 units?

  1. 6.5

  2. 12

  3. 2

  4. 6
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The triangle with sides 5, 12, 13 is a right triangle since 5² + 12² = 13². For any triangle, the inradius r = A/s where A is the area and s is the semi-perimeter. Here, s = (5+12+13)/2 = 15 and A = (5×12)/2 = 30, so r = 30/15 = 2 units. Options A (6.5) and D (6) are not the inradius; B (12) is the longest side, not the inradius.

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