31*19.97+199.7*6.8+199.7*0.1= 简算

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31*19.97+199.7*6.8+199.7*0.1= 简算

=(31/10)*(19.97*10)+199.7*6.8+199.7*0.1
=3.1*199.7+199.7*6.8+199.7*0.1
=199.7*(3.1+6.8+0.1)
=199.7*10
=1997

原式=31*19.97+19.97*10*6.8+19.97*10*0.1
=31*19.97+68*19.97+19.97
=19.97*(31+68+1)
=1997

=31*19.97+19.97*68+19.97*1=19.97*(31+68+1)=1997

=199.7*(3.1+6.8+0.1)=199.7*10=1997