một khối lập phương có cạnh a = 20cm bây giờ người ta khoét một lỗ trên khối lập phương có thể tích 4 đề xi mét khối.Roi nhet đay vào đó một chất có khối lượng riêng là 200 kg / mét khối Tìm khối lượng riêng của khối lập phương lúc này câu 2 một quả cầu đặc bằng kim loại có thể tích 5 đề xi mét khối và có khối lượng 44,5 kg a,tính khối lượng riêng của quả cầu b,tính trọng lượng riêng của chất làm quả cầu c,quả cầu thứ hai cùng chất cùng kích thước hình dạng giống hệt quả cầu trên nhưng có một lỗ rỗng bên trong và có khối lượng là 17,8 kg .Tính thể tích phần rỗng Làm chắc câu c giúp mình nha mọi người

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