8.7×9.9
=8.7×(10-0.1)
=8.7×10-8.7×0.1
=87-0.87
=86.13
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解:8.7×9.9=8.7×﹙10-0.1﹚
=8.7×10-8.7×0.1
=87-0.87
=86.13
8.7x9.9
=8.7×(10-0.1)
=8.7×10-8.7×0.1
=87-0.87
=86.13
=87*99/100=87*(100-1)/100
=(8700-87)/100=8613/100=86.13