Q.A wire of length 10 cm is bent so as to form an arc of a circle of radius 4 cm. What is the angle subtended at the centre in degrees?

Step 1: $\theta = \frac{s}{r} = \frac{10}{4} = 2.5$ radian.

Step 2: Convert to degree: $2.5\times\frac{180}{\pi}=\frac{450}{\pi} \approx 143.24°$ (using $\pi\approx\frac{22}{7}$: $\frac{450\times7}{22}=\frac{3150}{22}\approx143.18°$, …

• Treating the 10 cm wire length as the radius instead of the arc length.
• Forgetting the θ obtained from s/r is already in radian and needs converting to deg …