Question

The area of ring is 418 cm'. If the radius of the inner smaller circle is 6 cm, find the
radius of the bigger circle.​

Answer 1

Given :-

• The area of ring is 418 cm². If the radius of the inner smaller circle is 6 cm.

To find :-

• Radius of the bigger circle

Solution :-

• Area of ring = 418 cm²
• Radius of the inner smaller circle = 6cm

→ Area of bigger circle - Area of smaller circle

Let the radius of bigger circle be R and smaller circle be r

• According to question

→ πR² - πr² = 418

→ π(R² - r²) = 418

→ π[R² - (6)²] = 418

→ 22/7[R² - 36] = 418

→ 22[R² - 36] = 418 × 7

→ R² - 36 = 418 × 7/22

→ R² - 36 = 19 × 7

→ R² - 36 = 133

→ R² = 133 + 36

→ R² = 169

→ R = √169

→ R = 13 cm

Hence,

• Radius of bigger circle is 13 cm

Answer 2

Answer:

• Radius of the bigger circle is 13cm.

Step-by-step explanation:

Given that,

• Area of ring = 418 cm²
• Radius of the inner smaller circle = 6cm

According to Question,

Let the radius of bigger circle be R and smaller circle be r.

↪ Area of bigger circle - Area of smaller circle = Area of ring

[ Putting values ]

$\implies$ πR² - πr² = 418

$\implies$ π(R² - r²) = 418

$\implies$ π(R² - 6²) = 418

$\implies$ 22(R² - 36) = 418 × 7

$\implies$ 22R² - 792 = 2926

$\implies$ 22R² = 2926 + 792

$\implies$ 22R² = 3718

$\implies$ R² = 169

$\implies$ R = 13 cm $\red\bigstar$