Bài 4. Tính bằng cách thuận tiện nhất:
215 x 12 + 38 x 215 3450 x 15 – 3450 x 5
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215(12 + 38) = 215.50 = 10750
3450(15 - 5) = 3450.10 = 34500
215(12 + 38) = 215.50 = 10750
3450(15 - 5) = 3450.10 = 34500
