- 15 cm
- 30 cm
- 45 cm
- 60 cm

Option 2 : 30 cm

**Calculation:**

**Here r and 2r are diameters of circles,**

Diameter of bigger circle = r + 2r = 3r

Area of the bigger circle before cut = π(3r)^{2}/4

⇒ 9πr^{2}/4

Area of cut portion = π(r)2/4 + π(2r)2/4

⇒ 5πr^{2}/4

Area of uncut portion = 9πr2/4 - 5πr2/4

⇒ πr^{2}

**∴ πr ^{2} = 100 π**

⇒ r = 10 cm

**Diameter of bigger circle = 3r**

**⇒ 3 × 10 = 30 cm**

In question itself given that the diameters are r and 2r, don't confuse with usual notations in the calculation.

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