Question

calculate (a) the circumference of a circle of radius 3.5cm and (b) area of a circle of radius 4.65cm..

Answer 1

Answer:

(a) The circumference of a circle of radius 3.5cm is 0.22m.

(b) The area of a circle of radius 4.65cm is 0.679×10⁻²m².

Explanation:

CASE A: Circumference of the circle

• The measurement of the circle's boundaries is known as the circumference or perimeter of the circle. It is calculated as,

                                       $\mathrm{C=2\pi r}$      (1)

Where,

C=circumferance of the circle

r=radius of the circle

From the question the radius of the circle(r)=3.5cm=3.5×10⁻²m

By inserting the value of "r" in equation (1) we get;

$\mathrm{C=2\times \frac{22}{7}\times 3.5\times 10^{-2}}$

$\mathrm{C=22\times 10^{-2}\ m=0.22\ m}$      (2)

So, the circumference of the circle is 0.22m.

CASE B: Area of the circle

• The territory surrounded or covered by a circle's circumference is considered to be its area. To determine how much space is filled by a circular field or plot, use the area of the circle formula as given below:

                                        $\mathrm{A=\pi r^2}$        (3)

Where,

A=area of the circle

r=radius of the circle

From the question the radius of the circle(r)=3.5cm=4.65×10⁻²m

By inserting the value of "r" in equation (3) we get;

$\mathrm{A=\frac{22}{7}\times (4.65\times 10^{-2})^2}$

$\mathrm{A=67.9\times 10^{-4}}$

$\mathrm{A=0.679\times 10^{-2}\ m^2}$     (4)

So, the area of the circle is 0.679×10⁻²m².

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