A chord of the larger among two concentric circles is of length 10 cm and it is tangent to the smaller circle. What is the area (in cm2) of the annular portion between the two circles?
Answer & explanation
Correct answer: option 3
R = radius of the bigger circle
r = radius of the smaller circle
AB = 10 cm
then, AM = 5 cm
In ΔOAM , OA2 = OM2 + AM2
R2 = r2 + 52
R2 – r2 = 25
We already know that,
Area between the two circle = π (R2 – r2) = 25 π