Question

Two concentric circles have radii 21 cm and 42 cm.If angle AOB =60°,find area of shaded region.

Answer 1

first see,
area of the ring = π (42² - 21²) = 4158 cm²
now, we have to remove some parts,
that part = (sector formed by bigger circle) -( sector formed by smaller circle)
              =π (42)²×60°/360 -π(21)² ×60°/360°
              =(π/6)×(42² -21²) = 693 cm²
so the required area = 4158 - 693 = 3465 cm²

see, if small part is shaded then the answer is 693 cm² otherwise if red shaded region you wanna then above answer is correct.

Answer 2

hey your answer with full calculation