A chord of the larger among two concentric circles is of length 20 cm, and it is tangent to the smaller circle. What is the area (in cm2) of the annular portion between the two circles?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. 100π.
Let the radius of the bigger circle be R cm and the radius of the smaller circle be r cm
⇒ PS = 20/2 = 10 cm
In △OSP
⇒ OP2 = OS2 + PS2
⇒ R2 = r2 + 102
⇒ R2 - r2 = 100
The area of the annular portion between the two circles = π(R2 - r2) = 100π