题目内容
17.计算题(要写出计算过程)180000÷25÷32÷125
9999×9999+19999
$\frac{1}{1×4}$+$\frac{1}{4×7}$+…+$\frac{1}{97×100}$
$\frac{567+345×566}{567×345+222}$.
分析 (1)根据除法的性质得到原式=180000÷(25×32×125),再变形为180000÷[(25×4)×(8×125)]简便计算即可求解;
(2)变形为9999×9999+9999+10000,再根据乘法分配律简便计算;
(3)先拆项,再抵消法计算即可求解;
(4)先根据乘法分配律变形为$\frac{567+345×566}{566×345+345+222}$,再整体约分即可求解.
解答 解:(1)180000÷25÷32÷125
=180000÷(25×32×125)
=180000÷[(25×4)×(8×125)]
=180000÷(100×1000)
=180000÷100000
=1.8
(2)9999×9999+19999
=9999×9999+9999+10000
=9999×(9999+1)+10000
=9999×10000+10000
=(9999+1)×10000
=10000×10000
=100000000
(3)$\frac{1}{1×4}$+$\frac{1}{4×7}$+…+$\frac{1}{97×100}$
=$\frac{1}{3}$×(1-$\frac{1}{4}$+$\frac{1}{4}$-$\frac{1}{7}$+…+$\frac{1}{97}$-$\frac{1}{100}$)
=$\frac{1}{3}$×(1-$\frac{1}{100}$)
=$\frac{1}{3}$×$\frac{99}{100}$
=$\frac{33}{100}$
(4)$\frac{567+345×566}{567×345+222}$
=$\frac{567+345×566}{566×345+345+222}$
=$\frac{567+345×566}{566×345+567}$
=1
点评 分数巧算就是熟能生巧的过程,综合运用乘法分配律,分数化小数,小数化分数以及带分数化假分数、带分数拆分等方法达到巧算的目的.