19. Find the radius of the circle inscribed in a triangle of side lengths $50,120,130$.
19. Ans: 20
The triangle is a right triangle with area $A=5 \times 120 / 2=300$. The semiperimeter is $s=\frac{1}{2} \times(50+120+130)=150$. Hence the inradius is $A / s=20$.