Question

用简便方法计算下面各题． 9.8×25 0.3×2.5×0.4 2.3

用简便方法计算下面各题． 9.8×25 0.3×2.5×0.4 2.33×0.5×0.4×5 0.8×630×0.125 0.13×102 3.12×4+1.88×4．

Answer 1

（1）9.8×25
=（10-0.2）×25
=10×25-0.2×25
=250-5
=245；

（2）0.3×2.5×0.4
=0.3×（2.5×0.4）
=0.3×1
=0.3；

（3）2.33×0.5×0.4×5
=2.33×（5×0.4×0.5）
=2.33×1
=2.33；

（4）0.8×630×0.125
=（0.8×0.125）×630
=0.1×630
=63；

（5）0.13×102
=0.13×100+0.13×2
=13+0.26
=13.26；

（6）3.12×4+1.88×4
=（3.12+1.88）×4
=5×4
=20．