Question

The perimeter of a semi circle is 18 cm. Find its area

Answer 1

Answer:

Step-by-step explanation:

Perimeter of a circle = circumference of a circle

circumference of semi circle = 18 cm

1/2*2 Pi * r = 18 cm

pi*r = 18 cm

r = 18 / 22/7

r = 18 * 7/22

r = 63 / 11

Area of semi circle= 1/2 pi r^2

                              =1/2 * 22/7 * 63/11 * 63/11

                              = 9* 63/11

                              = 567/11

                              = 51.54 sq.cm

Answer 2

Answer :

Given :

• The perimeter of semi circle is 18 cm.

Find :

• The area of the semi circle.

Solution :

Let the radius be x,

$\dag$Formula for Perimeter of semi - circle

$\boxed{\bold {\dfrac {2×pi×radius}{2}}}$

$\:$

The perimeter of the semi-circle :-

➟ Perimeter =${\bold {\dfrac {2×\pi×radius}{2}}}$

➟18 = ${\bold{\dfrac {\dfrac{44}{7}×r}{2}}}$

➟18 × 2=${\bold { \dfrac{44}{7} × r}}$

➟36 = ${\bold {\dfrac {44}{7}}}$

➟${\bold {36 × \dfrac {7}{44}= r}}$

➟${\bold {36 × \dfrac {7}{44}= r}}$

➟${\bold { \dfrac {63}{11}= r}}$

➟${\bold { 5.72= r}}$

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$\dag$Formula for Area of semi - circle

$\boxed{\bold {\dfrac {pi×{radius}^{2}}{2}}}$

$\:$

The area of the semi - circle :-

➟ ${\bold {\dfrac {pi×{radius}^{2}}{2}}}$

➟ ${\bold {\dfrac {\dfrac {22}{7}×{5.72}^{2}}{2}}}$

➟ ${\bold {\dfrac {\dfrac {22}{7}×32.71}{2}}}$

➟ ${\bold {\dfrac{\dfrac {719.62}{7}}{2}}}$

➟ ${\bold {\dfrac {1439.14}{7}}}$

➟ ${\bold {205.60 \:cm\: square }}$

•°• The area of the semi circle is 205.06 cm square.

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