1. Tích của hai phân số trái dấu là một phân số âm (phân số có dấu “-“ đằng trước) đúng hay không? 2. Khi nhân một số nguyên c với phân số ta đem nhân c với tử rồi chia cho mẫu, như vậy có đúng không? 3. Tính chất của phép nhân phân số có giống tính chất của phép nhân số nguyên không? 4. Rút gọn từng phân số trước khi nhân có làm thay đổi kết quả không? II. Bài tập Bài 1. Tính: Bài 2. Thực hiện phép tính rồi rút gọn kết quả: Bài 3. Một kg gạo tẻ đổi được kg gạo nếp. Hỏi: 2 kg; kg; kg gạo tẻ đổi được bao nhiêu kg gạo nếp? giúp mik với ạ

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