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巧算 22.01+20.03+20.05+20.07+20.09+20.11+20.13

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巧算 22.01+20.03+20.05+20.07+20.09+20.11+20.13
22.01+20.03+20.05+20.07+20.09+20.11+20.13
巧算 22.01+20.03+20.05+20.07+20.09+20.11+20.13
法1:
基准数法:
22.01+20.03+20.05+20.07+20.09+20.11+20.13
=20×7+(0.01+0.03+0.05+0.07+0.09+0.11+0.13)+2
=140+(0.11+0.09)+(0.07+0.13)+(0.05+0.03+0.01)+2
=140+0.4+0.09+2
=142.49
法2:
等差数列:
22.01+20.03+20.05+20.07+20.09+20.11+20.13
=22.01+(20.03+20.05+20.07+20.09+20.11+20.13 )
=22.01+(20.03+20.13)×6÷2
=22.01+40.16×3
=22.01+120.48
=142.49