Question

The radius of a circle is 20 cm. It is divided into four parts of equal area by drawing three concentric circles inside it. Then, the radius of the largest of three concentric circles drawn is
(a)10√5 cm
(b)10√3 cm
(c)10√5 cm
(d)10√2 cm

Answer 1

Answer:

The radius of the largest of three concentric circle is 10√3 cm.

Among the given options option (b) 10√3 cm is the correct answer.

Step-by-step explanation:

Given :

Radius of a circle, OB (R) = 20 cm  

Let Radius of three concentric circles ,OA (r)= x cm.

Area of the 4th region = ¼ × Area the given circle

π(OB² - OA²) = ¼ × πR²

[Area of circular ring = π(R² - r²)]

(20² - x²) = ¼ × R²

400 - x² = ¼ × 20²

400 - x² = ¼ × 400

400 - x² = 100

400 - 100 = x²

x² = 300

x = √300

x = √100 × 3

x = 10√3

Radius of the largest of three concentric circle = 10√3 cm

Hence, the radius of the largest of three concentric circle is 10√3 cm.

HOPE THIS ANSWER WILL HELP YOU….

Answer 2

ANSWER IS

10 root 3

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