Question

用简便方法计算： 1.2×0.25+2.8×0.25 0.65×104 &nbs...

用简便方法计算： 1.2×0.25+2.8×0.25 0.65×104 3.2×1.25×2.5 1.25×8.08 5.6÷0.35 16.8÷40÷0.25．

Answer 1

1.2×0.25+2.8×0.25      
=（1.2+2.8）×0.25
=4×0.25
=1

0.65×104
=0.65×（100+4）
=0.65×100+0.65×4
=65+2.6
=67.6

3.2×1.25×2.5
=4×0.8×1.25×2.5
=（4×2.5）×（0.8×1.25）
=10×1
=10

1.25×8.08
=1.25×（8+0.08）
=1.25×8+1.25×0.08
=10+0.1
=10.1

5.6÷0.35
=5.6÷（0.7×0.5）
=5.6÷0.7÷0.5
=8÷0.5
=16

16.8÷40÷0.25
=16.8÷（40×0.25）
=16.8÷10
=1.68