Diện tích hình tròn là:
30 x 30 x 3,14 = 2826 (cm2)
Diện tích phần mũi tên là:
2826 x 20% = 565,2 (cm2)
Diện tích phần còn lại là:
2826 - 565,2 = 2260,8 (cm2)
Đs...
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