Question

the area between a concentric circle is 1540cm². If the radius of the outer circle is 21 cm, calculate the radius of the inner circle​

Answer 1

Correct Question:

The area enclosed between the concentric circles is 770 cm². If the radius of the outer circle is 21 cm, find the radius of the inner circle.

Answer:

• The radius of the inner circle is 14 cm.

Step-by-step explanation:

Given that:

• The area between a concentric circle is 770 cm².
• The radius of the outer circle is 21 cm.

To Find:

• The radius of the inner circle.

Let us assume:

• The radius of the inner circle be x.

Formula:

• Area between a concentric circle = π(R² - r²)

Where,

• R = The radius of the outer circle
• r = The radius of the inner circle

Finding the radius of the inner circle:

According to the question.

⟶ π(21² - x²) = 770

⟶ π(441 - x²) = 770

⟶ 441 - x² = 770/π

⟶ 441 - x² = (770 × 7)/22

⟶ 441 - x² = 245

⟶ x² = 441 - 245

⟶ x² = 196

⟶ x = √196

⟶ x = 14

∴ The radius of the inner circle = 14 cm

Answer 2

Answer:

Appropriate Question :-

the area between a concentric circle is 770 cm². If the radius of the outer circle is 21 cm, calculate the radius of the inner circle

Given :-

• Area between two concertic circle = 770 cm²
• Radius of outer circle = 21 cm

To Find :-

Radius of inner circle

Solution :-

Let the radius be r

Area between the two circle = πR² - πr²

Taking π as common

π(R² - r²) = 770

[(21)² - (r²)] = 770 × 7/22

[441 - r²] = 245

441 - 245 = r²

196 = r²

√196 = √r²

14 = r