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

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