如题所述
27×99
=27X(100-27)
=27X100-27
=2700-27
=2673
49+49×49
=49X(1+49)
=49X50
=2450
39×101-39
=39X(101-1)
=39X100
=3900
99×64+64
=64X(99+1)
=64X100
=6400
=27X(100-27)
=27X100-27
=2700-27
=2673
49+49×49
=49X(1+49)
=49X50
=2450
39×101-39
=39X(101-1)
=39X100
=3900
99×64+64
=64X(99+1)
=64X100
=6400
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