Question

Length of tape required to cover the edges of a semicircular disc of radius $10cm$ is

• A. $62.8cm$
• B. $51.4cm$
• C. $31.4cm$
• D. $15.7cm$

Answer 1

The correct option is B

$51.4cm$

Evaluate the perimeter of a semi-circle :

To cover the edges of a semicircular disc tape, the perimeter is required.

Perimeter of a semicircle $=$ Circumference of semicircle $+$ Diameter

Circumference of a semicircle$=\mathrm{\pi r}$

Assumption : $\mathrm{\pi }=3.14$

$\therefore$ Circumference of the circle $=3.14\times 10$

$=31.4cm$

Diameter$=2r$

$=20cm$

$\therefore$ Perimeter of the semicircle$=31.4+20$

$=51.4cm$

Thus, tape of length $51.4cm$ is required.

Hence option $\left(B\right)$ $51.4cm$, is the correct answer.