13.9*138/137+137*1138/1=( - 知识问答

13.9*138/137+137*1138/1=(简便算法)

8个回答

13.9 * 137/138 + 137 * (1 + 1/138)
= 13.9 * 137/138 + 137 * 139/138
= 11/10 * 137 * 139/138
= 1.1 * 137 * 139/138
= 1.1 * (138 -1) * (138+1)/138
= 1.1 * (138^2 -1)/138
= 1.1 * (138 - 1/138)
= 151.8 - 11/1380
= 151.792

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