1.2*5.6+6.5*2.1 简便算法
问题描述：
1.2*5.6+6.5*2.1 简便算法
答
1.2(5+0. 6)+6.5(2+0.1)
=6+0.72+13+0.65
=19+1.37
=20.37
答
原式=(0.3*4)*(7*0.8)+6.5*(0.3*7)
=(0.3*7)*(4*0.8+6.5)
=2.1*9.7
=2.1*(10-0.3)
=2.1*10-2.1*0.3
=21-0.63
=20.37