The lenghth of a side equilateral tringle is 18cm. The area ( in cm2) of the region lying between the circumcircle and incircle of tringle is [use pi = 22/7]
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e 254.
Side of the equilateral triangle = 18 cm
Radius of circum - circle R = 18/√3 cm
Radius of in - circle r = 18/2√3 = 9/√3 cm
The area of the region lying between the circumcircle and incircle of tringle = π (R2 – r2)
= π (R + r) (R-r)
= (22/7) × (18/√3 + 9/√3) (18/√3 - 9 /√3)
= (22/7) × 27/√3 × 9/√3
= (81 × 22)/7
= 1782/7 cm²
=254(4/7) cm2