题目内容
用计算器计算与探究.
(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=
(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=
分析:先运用计算器计算时算式的结果,再找出规律即可.
解答: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;
通过计算发现:因数每增加一个0.5,乘积的小数位数就增加一位.
(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.
通过计算发现:因数每增加一个0.2,乘积的小数位数就增加一位.
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;
通过计算发现:因数每增加一个0.5,乘积的小数位数就增加一位.
(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.
通过计算发现:因数每增加一个0.2,乘积的小数位数就增加一位.
点评:先正确的运用计算器,得出乘积,再根据乘积的变化找出规律.
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