Question 12 Marks
>In figure 7.35, □PQRS is a rectangle. If PQ = 14 cm, QR = 21 cm, find the areas of the parts x, y and z.


Answer
View full question & answer→Since part x is a sector of a circle with radius, $\mathrm{r}=14 \mathrm{~cm}$ and the central angle is $90^{\circ}$, so the area of x will be equal to one-fourth of the area of circle with PQ as radius.
Area of circle with $P Q$ as radius $=\pi(P Q)^2$
$\Rightarrow x=\frac{1}{4} \times \pi \times P Q^2$
$\Rightarrow x=\frac{1}{4} \times \frac{22}{7} \times 14^2$
$\Rightarrow \mathrm{x}=154 \mathrm{sq} . \mathrm{cm}$
Similarly, area $y$ is also equal to one-fourth od area of circle with radius, $r=Q R-P Q$
$\Rightarrow r=21-14=7 \mathrm{~cm}$
Area of circle with $r$ as radius $=\pi(r)^2$
$\Rightarrow y=\frac{1}{4} \times \pi \times r^2$
$\Rightarrow y=\frac{1}{4} \times \frac{22}{7} \times 7^2$
$\Rightarrow \mathrm{y}=38.5 \mathrm{sq} . \mathrm{cm}$
Also,
$z=\text { Area of rectangle(PQRS) }-x-y$
Area of rectangle $=P Q \times Q R$
$\Rightarrow \text { Area of rectangle }=14 \times 21=294 \text { sq. } \mathrm{cm}$
$\Rightarrow z=294-154-38.5$
$\Rightarrow z=101.5 \mathrm{sq} . \mathrm{cm}$
$\therefore$ the area of $x, y$ and $z$ are 154 sq.cm, 38.5 sq.cm and $101.5 \mathrm{sq} . \mathrm{cm}$ respectively
Area of circle with $P Q$ as radius $=\pi(P Q)^2$
$\Rightarrow x=\frac{1}{4} \times \pi \times P Q^2$
$\Rightarrow x=\frac{1}{4} \times \frac{22}{7} \times 14^2$
$\Rightarrow \mathrm{x}=154 \mathrm{sq} . \mathrm{cm}$
Similarly, area $y$ is also equal to one-fourth od area of circle with radius, $r=Q R-P Q$
$\Rightarrow r=21-14=7 \mathrm{~cm}$
Area of circle with $r$ as radius $=\pi(r)^2$
$\Rightarrow y=\frac{1}{4} \times \pi \times r^2$
$\Rightarrow y=\frac{1}{4} \times \frac{22}{7} \times 7^2$
$\Rightarrow \mathrm{y}=38.5 \mathrm{sq} . \mathrm{cm}$
Also,
$z=\text { Area of rectangle(PQRS) }-x-y$
Area of rectangle $=P Q \times Q R$
$\Rightarrow \text { Area of rectangle }=14 \times 21=294 \text { sq. } \mathrm{cm}$
$\Rightarrow z=294-154-38.5$
$\Rightarrow z=101.5 \mathrm{sq} . \mathrm{cm}$
$\therefore$ the area of $x, y$ and $z$ are 154 sq.cm, 38.5 sq.cm and $101.5 \mathrm{sq} . \mathrm{cm}$ respectively








