Question

8. The area of circle is 38.5 sq cm. What will
be its circumference?
(1) 2.2 cm (2) 22 cm (3) 220 cm (4) 185 cm​

Answer 1

Answer:

(2) 22 cm

Step-by-step explanation:

Given:

• Area of circle = 38.5 cm²

To find:

• Circumference = ?

Formulas used:

1. Area of circle = πr²
2. Circumference of circle = 2πr

Solution:

In this question, we know the area of circle. First let us find out radius by applying the first formula.

Area of circle = πr²

⇒ 38.5 = 22r² ÷ 7

⇒ 38.5 × 7 = 22r²

⇒ r² = (38.5 × 7) ÷ 22

⇒ r² = 269.5 ÷ 22

⇒ r² = 12.25

⇒ r = √12.25

⇒ r = 3.5

So, the Radius = 3.5 cm

Circumference of circle = 2πr

➝ Circumference = 2 × π × 3.5

➝ Circumference = 7π

➝ Circumference = (22 ÷ 7) × 7

➝ Circumference = 22 cm

∴ Circumference of circle = 22 cm

Answer 2

$\huge \tt \pink { question}$

The area of circle is 38.5 sq cm. What will

be its circumference?

(1) 2.2 cm (2) 22 cm (3) 220 cm (4) 185 cm

$\huge \tt \pink { options}$

(1) 2.2 cm

(2) 22 cm✅✅

(3) 220 cm

(4) 185 cm

$\huge \tt \pink { solution}$

Area of circle = πr²

38.5 = 22r² ÷ 7

38.5 × 7 = 22r²

r² = (38.5 × 7) ÷ 22

r² = 269.5 ÷ 22

r² = 12.25

r = √12.25

⇒ r = 3.5

So, the Radius = 3.5 cm

Circumference of circle = 2πr

Circumference = 2 × π × 3.5

Circumference = 7π

Circumference = (22 ÷ 7) × 7

= Circumference = 22 cm

∴ Circumference of circle = 22 cm

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