Explanation:
The area of circle with radius 4cm is,
area of circle = π r *r = 3.14 * 4 * 4
= approx 50.27
The area of circle with radius 2cm is,
area of circle = π * r * r = 3.14 * 2 * 2
= approx 12.57
The circles are concentric means they have a common Centre, so,
Area between the two circles = area of bigger circle - area of smaller circle
= 50.27 - 12.57
= 37. 7 sq. cm