算一算:25×198 用简便方法计算:99×64±64
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算一算:25×198 用简便方法计算:99×64±64
25x198
=25x(200-2)
=25x200-25x2
=5000-50
=4950;
99x64+64?
=64x(99+1)
=64x100
=6400
=25x(200-2)
=25x200-25x2
=5000-50
=4950;
99x64+64?
=64x(99+1)
=64x100
=6400