Question

用計算器計算與探究．
（1）5×0.5=
5×0.5×0.5=
5×0.5×0.5×0.5=
5×0.5×0.5×0.5×0.5=
（2）9×0.2=
9×0.2×0.2=
9×0.2×0.2×0.2=
9×0.2×0.2×0.2×0.2=

Answer 1

解：（1）5×0.5=2.5，
5×0.5×0.5=1.25，
5×0.5×0.5×0.5=0.625，
5×0.5×0.5×0.5×0.5=0.3125；
通過計算發(fā)現(xiàn)：因數(shù)每增加一個0.5，乘積的小數(shù)位數(shù)就增加一位．

（2）9×0.2=1.8，
9×0.2×0.2=0.36，
9×0.2×0.2×0.2=0.072，
9×0.2×0.2×0.2×0.2=0.0144．
通過計算發(fā)現(xiàn)：因數(shù)每增加一個0.2，乘積的小數(shù)位數(shù)就增加一位．
分析：先運用計算器計算時算式的結果，再找出規(guī)律即可．
點評：先正確的運用計算器，得出乘積，再根據(jù)乘積的變化找出規(guī)律．