Question

6．計算下面各題，能簡算的要簡算．

①21.12+1.5×5-6.02	②6.2×1.18+0.82×6.2
③3.6÷[（1.2+0.24）×5]	④10.1×6.7
⑤4-3.25÷1.3×0.7	⑥0.25×1.25×3.2

Answer 1

分析 ①先算乘法，然后從左往右依次運算；
②運用乘法分配律簡算；
③先算小括號內的伽法，再算中括號內的乘法，最后算括號外的除法；
④把10.1看做10+0.1，運用乘法分配律簡算；
⑤先算除法和乘法，再算減法；
⑥把3.2看作8×0.4，運用乘法分配律簡算．

解答 解：①21.12+1.5×5-6.02
=21.12+7.5-6.02
=28.62-6.02
=22.6

②6.2×1.18+0.82×6.2
=6.2×（1.18+0.82）
=6.2×2
=12.4

③3.6÷[（1.2+0.24）×5]
=3.6÷[1.44×5]
=3.6÷7.2
=0.5

④10.1×6.7
=（10+0.1）×6.7
=10×6.7+0.1×6.7
=67+0.67
=67.67

⑤4-3.25÷1.3×0.7
=4-2.5×0.7
=4-1.75
=2.25

⑥0.25×1.25×3.2
=0.25×1.25×8×0.4
=（0.25×0.4）×（1.25×8）
=0.1×10
=1

點評 此題考查了小數的四則混合運算，注意運算順序和運算法則，靈活運用所學的運算定律簡便計算．