9.98×9.9、2.6×9.8和6.28×9.9+0.628的简便计算

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9.98×9.9、2.6×9.8和6.28×9.9+0.628的简便计算
9.98×9.9、2.6×9.8和6.28×9.9+0.628的简便计算

9.98×9.9、2.6×9.8和6.28×9.9+0.628的简便计算
9.98×9.9
=9.98×(10-0.1)
=99.8-0.998
=98.802
2.6×9.8
=2.6×(10-0.2)
=26-0.52
=25.48
6.28×9.9+0.628
=6.28×(9.9+0.1)
=6.28×10
=62.8