21×17/20(简便算法) 19/54×53(简便运算)

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21×17/20(简便算法) 19/54×53(简便运算)
21×17/20(简便算法) 19/54×53(简便运算)

21×17/20(简便算法) 19/54×53(简便运算)
21×17/20
=(20+1)×17/20
=20×17/20+1×17/20
=17+17/20
=17又17/20
19/54×53
= 19/54×(54-1)
=19/54×54-19/54×1
=19-19/54
=18+(1-19/54)
=18又35/54

(20+1)x 17 /20 = 17 + 17/20
19 x(54-1)/54 = 19 -19/54

21×17/20=(20+1)·17/20=17+17/20=17又17/20
19/54x53=19/54(54-1)=19-19/54=18又35/54

21X17/20=(1+20)X17/20然后去括号
=17/20+17=17又17/20
19/54X53=19/54X(54-1)再去括号
=19/54X54-19/54=19-19/54=18又35/54

化成一样的去掉分母