Question

On area and circumference (perimeter) of circle find the area and perimeter of a circle when its radius = 3.5 cm.
$(take \: \pi = \frac{22}{7} )$

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Answer 1

Given radius = 3.5 cm.

We know that Area of circle = πr^2

⇒ (22/7) * (3.5)^2

⇒ 22 * 1.75

⇒ 38.5 cm^2.

(ii)

We know that Perimeter of circle = 2πr

⇒ 2 * (22/7) * 3.5

⇒ 2 * 22 * 0.5

⇒ 22 cm.

Therefore:

⇒ Area = 38.5 cm^2

⇒ Perimeter = 22 cm.

Hope it helps!

Answer 2

Formulas related to the area and circumference of the circle are given below : -

$\mathsf{\bold{\boxed{Area\:=\pi r^2}}}$

$\mathsf{\bold{\boxed{Circumference\:= 2 \pi r\:\:Or\:\:\pi d}}}$

Where r is the radius and d is the diameter( 2 x radius ).

Solution : -

Radius of the circle = 3.5 cm Or 35 / 10

  On the basis of the formulas given above,

Area of the circle = πr^2

⇒ $\dfrac{22}{7}\times \bigg(\dfrac{35}{10}\bigg)^2$

⇒ $\dfrac{22}{7} \times \dfrac{35}{10} \times \dfrac{35}{10}$

⇒ $\dfrac{22\times35\times\35}{7\times10\times10}$

⇒ 38.5 cm^2

Perimeter of the circle = 2πr

⇒ 2 x $\dfrac{22}{7}$ x $\dfrac{35}{10}$

⇒ 2 x 11 cm

⇒ 22 cm

Therefore, area of the given circle = 38.5 cm^2

Perimeter of the given circle = 22 cm.