0.7乘1.25乘0.9简便计算 急急急!!!!!!!!!!
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0.7=0.8-0.1
0.9=0.8+0.1
代入题目给的式子中:
得:
(0.8-0.1)×(0.8+0.1)×1.25
=(0.8²-0.1²)×1.25
=1.25×0.8×0.8-1.25×0.01
=1×0.8-0.0125
=0.8-0.0125
=0.7875
0.9=0.8+0.1
代入题目给的式子中:
得:
(0.8-0.1)×(0.8+0.1)×1.25
=(0.8²-0.1²)×1.25
=1.25×0.8×0.8-1.25×0.01
=1×0.8-0.0125
=0.8-0.0125
=0.7875
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