Question

五、用简便方法计算.（要写出简算过程） 1.9＋19.9＋199.9＋0.3 0.25×12.5×3.2 457÷25÷

Answer 1

1.9＋19.9＋199.9＋0.3 =2-0.1+20-0.1+200-0.1+0.3=2+20+200-0.3+0.3=222

0.25*12.5*3.2

=0.25*4*12.5*3.2/4=1*12.5*0.8=10

457÷25÷4 =457/（25×4）=457/100=4.57

6.8-1.36-1.64=6.8-3=3.8