A line cuts two concentric circles. The lengths of chords formed by that line on the two circles are 4 cm and 16 cm. What is the difference (in cm2 ) in squares of radii of two circles?

For chords in concentric circles, if a line cuts both circles, the perpendicular distance from the center to the chord is the same for both circles. Let this distance be d. For the smaller circle: (4/2)² + d² = r², so r² = 4 + d². For the larger circle: (16/2)² + d² = R², so R² = 64 + d². Difference in squares of radii = R² - r² = (64+d²) - (4+d²) = 60.