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用简便方法计算(1)0.9999×0.7+0.1111×2.7;(2)(1+0.228-0.21)×(0.228-0.21+0.2003)-(1+0.228-0.21+0.2003)×(0.228-0.21)
题目详情
用简便方法计算
(1)0.9999×0.7+0.1111×2.7;
(2)(1+0.228-0.21)×(0.228-0.21+0.2003)-(1+0.228-0.21+0.2003)×(0.228-0.21)
(1)0.9999×0.7+0.1111×2.7;
(2)(1+0.228-0.21)×(0.228-0.21+0.2003)-(1+0.228-0.21+0.2003)×(0.228-0.21)
▼优质解答
答案和解析
(1)0.9999×0.7+0.1111×2.7
=(0.1111×9)×0.7+0.1111×2.7
=0.1111×6.3+0.1111×2.7
=0.1111×(6.3+2.7)
=0.1111×9
=0.9999
(2)设1+0.228-0.21=a,0.228-0.21=b,
(1+0.228-0.21)×(0.228-0.21+0.2003)-(1+0.228-0.21+0.2003)×(0.228-0.21)
=a×(b+0.2003)-(a+0.2003)×b
=ab+0.2003a-ab-0.2003b
=0.2003×(a-b)
=0.2003×1
=0.2003
=(0.1111×9)×0.7+0.1111×2.7
=0.1111×6.3+0.1111×2.7
=0.1111×(6.3+2.7)
=0.1111×9
=0.9999
(2)设1+0.228-0.21=a,0.228-0.21=b,
(1+0.228-0.21)×(0.228-0.21+0.2003)-(1+0.228-0.21+0.2003)×(0.228-0.21)
=a×(b+0.2003)-(a+0.2003)×b
=ab+0.2003a-ab-0.2003b
=0.2003×(a-b)
=0.2003×1
=0.2003
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