A circle has a circumference of 25.12 units. What is its radius (approximately)?

A chord of length 16 cm is drawn in a circle of radius 10 cm. What is the distance of the chord from the center of the circle?

If the diameter of a circle is doubled, how does the area of the circle change?

Two circles have radii of 5 cm and 12 cm. What is the radius of a circle whose area is equal to the sum of the areas of these two circles?

A sector of a circle has a central angle of 60 degrees and a radius of 6 cm. What is the area of the sector?