如题所述
199x9
=(200-1)x9
=1800-9
=1791
278x99
=278x(100-1)
=27800-278
=27522
560x101
=560x(100+1)
=56000+560
=56560
=(200-1)x9
=1800-9
=1791
278x99
=278x(100-1)
=27800-278
=27522
560x101
=560x(100+1)
=56000+560
=56560
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