A. Most of the time on a number sense test the question will give you the sides of a right triangle and ask you to find the value of the radius of an inscribed circle. Here is a picture of what is happening:
B. Finding the radius is simple. Use the following formula:
r = a + b - c
2
C. Examples:
Ex [1] Find the radius of an inscribed circle of a 6, 8, 10 triangle.
a. The answer is 6+8-10/2 = 4/2 = 2.
Ex [2] Find the radius of an inscribed circle of a right triangle that has a leg of 14.
a. In this example, we will have to derive a Pythagorean triple.
b. We know that the triangle has sides of 14, 48, and 50.
c. The answer is 14+48-50/2 = 12/2 = 6.