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

2 thoughts on “the area between a concentric circle is 1540cm². If the radius of the outer circle is 21 cm, calculate the radius of the inner cir”

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

   Reply

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

   [tex] \\ [/tex]

   Reply