Question

用递等式计算（能简算的要简算）1.2×0.25+2.8×0.25 0.65×104  ...

用递等式计算（能简算的要简算）1.2×0.25+2.8×0.25 0.65×104 16.8÷40÷0.25 3.2×1.25×2.5 2.8×3.6+28×0.64 1.25×8.08 5.6÷0.35 20.9+10.5÷（5.2-4.5）

Answer 1

①1.2×0.25+2.8×0.25
=0.25×（1.2+2.8）
=0.25×4
=1；

②0.65×104
=0.65×（100+4）
=0.65×100+0.65×4
=65+2.6
=67.6；

③16.8÷40÷0.25
=16.8÷（40×0.25）
=16.8÷10
=1.68；

④3.2×1.25×2.5
=8×0.4×1.25×2.5
=（8×1.25）×（0.4×2.5）
=10×1
=10；

⑤2.8×3.6+28×0.64
=28×0.36+28×0.64
=28×（0.36+0.64）
=28×1
=28；

⑥1.25×8.08
=1.25×（8+0.08）
=1.25×8+1.25×0.08
=10+0.1
=10.1；

⑦5.6÷0.35
=5.6÷7÷0.05
=0.8÷0.05
=16；

⑧20.9+10.5÷（5.2-4.5）
=20.9+10.5÷0.7
=20.9+15
=35.9．