Question

Find area of a shaded portion, if radii of inner and outer circles are 3.5cm and 4.2cm.

Answer 1

Answer:

$\textbf{Area of the shaded portion=16.94\: cm^2 }$

Step-by-step explanation:

Find area of a shaded portion, if radii of inner and outer circles are 3.5cm and 4.2cm.

Given:

Inner radius, r=3.5 cm

Outer radius, R=4.2 cm

$\boxed{\textbf{Area of the shaded portion= \pi\:R^2-\pi\:r^2 }}$

$\implies\text{Area of the shaded portion= \pi(R^2-r^2) }$

$\implies\text{Area of the shaded portion= \pi(4.2^2-3.5^2) }$

$\implies\text{Area of the shaded portion= \pi(4.2-3.5)(4.2+3.5) }$

$\implies\text{Area of the shaded portion= \frac{22}{7}(0.7)(7.7) }$

$\implies\text{Area of the shaded portion=(22)(0.1)(7.7)}$

$\implies\text{Area of the shaded portion=(2.2)(7.7)}$

$\implies\textbf{Area of the shaded portion=16.94\: cm^2 }$