The circumference of two circles are in the ratio 4:5. If the area of the larger circle is 625 square units, find the area of the smaller circle.

A chord of length 16 cm is at a distance of 6 cm from the center of a circle. What is the length of the radius?

Two triangles, triangle XYZ and triangle LMN are such that XY = LM, YZ = MN, and XZ = LN. By which property are they congruent?