Question

脫式計算 7.8÷2.5÷4	640÷0.4÷0.2	8.3×9.9+0.83
8.48+2.6×3.2	0.78×15÷0.3	0.18÷0.24÷0.025．

Answer 1

分析：運(yùn)用四則混合運(yùn)算的順序進(jìn)行計算即可，含有兩級運(yùn)算，先做乘除后做加減．
計算7.8÷2.5÷4　把算式轉(zhuǎn)化成7.8÷（2.5×4）進(jìn)行計算；
8.3×9.9+0.83把算式轉(zhuǎn)化成8.3×9.9+8.3×0.1進(jìn)行計算．

解答：解：①7.8÷2.5÷4　
=7.8÷（2.5×4）
=7.8÷10
=0.78；

②640÷0.4÷0.2　
=1600÷0.2
=8000；

③8.3×9.9+0.83
=8.3×9.9+8.3×0.1
=8.3×（9.9+0.1）
=8.3×10
=83；

④8.48+2.6×3.2　
=8.48+8.32
=16.8；

⑤0.78×15÷0.3　
=11.7÷0.3
=39；

⑥0.18÷0.24÷0.025
=0.75÷0.025
=30．

點(diǎn)評：本題考查了運(yùn)算的順序，注意計算結(jié)果的小數(shù)點(diǎn)的位置．