Question

the rope.
- The area of a circle is 394•24 cm^2
Calculate : (i) the radius of the circle, Gi) the circumference of the circle.
Find the perimeter and area of a semi-circular plate of radius 25 cm (Take - 3.14)​

Answer 1

Step-by-step explanation:

i)A=pi×r^2 ; (394.24cm^2=0.039424 m^2)

r^2=0.039424 / 3.14 =0.0125 m or 1.25cm

ii)circumference =2×pi×r=2×3.14×0.0125=0.0785

A=pi×r^2 /2 =3.14×(0.25)^2 / 2=0.098125m^2 or 981.25cm^2

perimeter =r(pi+2)=0.25(3.14+2)=1.285 m or 128.5 cm

Answer 2

Step-by-step explanation:

area of circle = 394.24 cm²

therefore,

$\pi \: r ^{2} = \: 394.24 \: cm {}^{2}$

therefore

r² = (394.24 ÷ 3.14) cm²

r²= 125.55cm

therefore,

r =

$\sqrt{125.55} \: cm$

so, r = 11.20 cm

circumference =

$2\pi \: r$

= 2 × 3.14 x 11.20 cm

= 70.34 cm

IN THE CASE OF SEMI CIRCULAR PLATE..

radius = 25 cm

perimeter =

$(2\pi \: r \:) \div 2 + 2 \times \: r$

=

$\pi \: r \: + 2r$

= 3.14 × 25 + 50 cm

= 78.5 + 50 cm

= 128.5 cm

area of the semicircular plate =

$(\pi \: r { }^{2} )\div 2$

= (3.14 × 25 × 25)/2

= 981.25cm²