1.

A circular wire of radius 7.5 cm is cut and bent so as to tie along the circumference of a hoop whose radius is 120 cm. Find in degrees the angle which is subtended at the centre of the hoop.

Answer»

Radius of the circular wire = 7.5 cm 

∴ Length of the circular wire = 2π × 7.5 = \(\frac{1}{2}\) 15 π cm 

[∴ Circumference = 2πr] 

Radius of the hoop = 120 cm 

Let θ be the angle subtended by the wire at the centre of the hoop, Then, 

\(θ=\frac{arc}{radius}\Rightarrow θ = (\frac{15\pi}{120})°\)

\(=(\frac{\pi}{8})°=(\frac{\pi}{8}\times\frac{180}{\pi})°=22°30'\)



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