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The area of a circle is 10 square centimeters. If its radius is doubled, the area of the circle will be 10 square centimeters______ Square centimeter
The area of the circle is s = π R2, the radius is expanded by 2 times, the area is s = π (2R) 2 = π × 4r2 = 4 π R2, 4 π R2 △ π R2 = 4, that is, the area of the circle is expanded by 4 times; 10 × 4 = 40 (square centimeter), answer: the area of the circle becomes 40 square centimeter
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