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9.9×9.9+19.9 简便计算
人气:189 ℃ 时间:2020-04-10 10:23:15
解答
9.9×9.9+19.9
=9.9×(10-0.1)+19.9
=9.9×10-9.9×0.1+19.9
=99-0.99+19.9
=99+18.91
=117.91
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