Ex.11.3 Q7 Perimeter and Area - NCERT Maths Class 7

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Find the perimeter of the adjoining figure, which is a semicircle including its diameter

Text Solution

What is known?

Diameter of the semicircle.

What is unknown?

The perimeter of the semicircle including its diameter.


To find the perimeter of the given figure, add the circumference or perimeter of the semi-circle and the diameter of the given figure.


Given, diameter \(= 10 \rm\,cm\)

Radius \(\begin{align}=\frac{{10}}{2}\end{align}= 5 \rm\,cm\)

Perimeter of the given figure \(=\) Circumference of semi \(-\) circle \(+\) diameter

\[\begin{align}&= \frac{{2\pi r}}{2} + {\text{D}} \\{\text{ }}&= \pi r + {\text{D}} \\&= \frac{{22}}{7} \times 5 + 5 \\&= \frac{{110}}{7} + 5 \\&= 25.71\;\rm cm\end{align}\]

Thus, the perimeter of the given figure is \(25.71\rm\, cm.\)