Question

18．計(jì)算，能簡(jiǎn)算的要簡(jiǎn)算．
①125×25×8
②101×55
③8.9dm+1m
④12.5÷0.5×3.2
⑤48.65-25-23．

Answer 1

分析 ①利用乘法交換律與結(jié)合律計(jì)算；
②利用乘法的分配律計(jì)算；
③把8.9dm轉(zhuǎn)化成1m-0.1m再計(jì)算；
④利用乘法交換律與結(jié)合律計(jì)算；
⑤利用減法性質(zhì)計(jì)算．

解答 解：①125×25×8
=（125×8）×25
=1000×25
=25000

②101×55
=（100+1）×55
=100×55+1×55
=5500+55
=5555

③8.9dm+1m
=1m-0.11m+1m
=（1m+1m）-0.11m
=2m-0.11m
=1.89m

④12.5÷0.5×3.2
=12.5÷0.5×0.8×4
=（12.5×0.8）×4÷0.5
=10×4÷0.5
=80

⑤48.65-25-23
=48.8-（25+23）
=48.8-48
=0.8

點(diǎn)評(píng) 考查學(xué)生對(duì)四則運(yùn)算法則以及運(yùn)算定律和運(yùn)算性質(zhì)的掌握情況．