0.42X9.9+0.042 12.5X（100+0.8） 12X0.75/2.5 简便运算怎么算?
问题描述：
0.42X9.9+0.042 12.5X（100+0.8） 12X0.75/2.5 简便运算怎么算?
答
0.42X9.9+0.042
=0.42*（9.9+0.1）
=0.42*10
=4.2
12.5X（100+0.8）
=1250+10
=1260
12X0.75/2.5
=1.2*7.5/2.5
=1.2*3
=3.6
答
(1)0.42x9.9+0.42x0.1
=0.42x(9.9+0.1)
=0.42x10
=4.2
(2)12.5x100+12.5x0.8
=1250+10
=1260
(3)3x4x1/4x0.75
=3x0.75
=2.25
答
0.42X9.9+0.042
=0.42×9.9+0.42×0.1
=0.42×(9.9+0.1)
=0.42×10
=4.2
12.5X（100+0.8）
=12.5×100+12.5×0.8
=1250+10
=1260
12X0.75/2.5
=12×(0.75/2.5)
=12×0.3
=0.36