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98x199用巧算怎么做

原式=98×(200-1) =98×200-98×1 =19600-98 =19600-100+2 =19500+2 =19502

原式=98×(200-1) =98×200-98×1 =19600-98 =19600-100+2 =19500+2 =19502

200*119-119*2

(200-2+0.2-0.002)x(200-1)-(200-1+0.2-0.001)(200-2) =(200-2)x(200-1)+(0.2-0.002)x(200-1)-(200-1)x(200-2)-(0.2-0.001)x(200-2) =(0.2-0.002)x(200-1)-(0.2-0.001)x(200-2) =(40-0.2-0.4+0.002)-(40-0.4...

123×199 =123x(200-1) =123x200-123 =24600-123 =24477

=489*(1+199) =489*200 =97800

巧算 2999×1.998-199.8×9.99 =29.99×199.8-199.8×9.99 =(29.99-9.99)×199.8 =20×199.8 =2×1998 =2×(2000-2) =4000-4 =3996

982-199怎么巧算? =982-200+1 =782+1 =783

原式=99*100-99*1-199 =99*100-100+1-200+1 =9602

解: 99×99+199 =99×99+100+99 =99×(99+1)+100 =9900+100 =10000

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