Using arc length formula (θ / 360) x 2 x π x r gives: (i) (60/360) x 2 x (22/7) x 3.5 = 11/3 = 3.67 cm, and (ii) (120/360) x 2 x (22/7) x 6.3 = 13.2 m.
Calculate the length of the arc of a circle if: (i) the radius is 3.5 cm and the angle at the centre is 60°, and (ii) the radius is 6.3 m and the angle at the centre is 120°.
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Arc length formula is l = 2 x π x r x (θ / 360).
(i) Given r = 3.5 cm = 7/2 cm, θ = 60°:
l = 2 x (22/7) x (7/2) x (60/360) = 22 x (1/6) = 11/3 cm = 3.67 cm.
(ii) Given r = 6.3 m = 63/10 m, θ = 120°:
l = 2 x (22/7) x (63/10) x (120/360) = (44/7) x (63/10) x (1/3) = (44 x 9) / (10 x 3) = (44 x 3) / 10 = 132/10 = 13.2 m.
For more NCERT Solutions of Class 9 Ganita Manjari Chapter 6 Measuring Space: Perimeter and Area Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/maths/ganita-manjari-chapter-6/