题目内容
能简便的用简便方法计算.
①(0.7×-0.11×)÷0.125
②15.17-(+4.97)-0.4
③÷+÷
④999×1999+999
⑤(-)÷(×)
解:①(0.7×-0.11×)÷0.125,
=(×-×)÷,
=(-)×8,
=×8,
=3;
②15.17-(3+4.97)-0.4,
=15.17-3.6-4.97-0.4,
=(15.17-4.97)-(3.6+0.4),
=10.2-4,
=6.2;
③÷+÷,
=×+×5,
=+,
=3;
④999×1999+999
=999×(1999+1),
=999×2000,
=1998000;
⑤(-)÷(×),
=÷,
=×,
=.
分析:①把0.7×看做×,0.11×看做×,先算括号里的,再算括号外面÷0.125看做除以;
②把原算式变成15.17-3.6-4.97-0.4,然后变成(15.17-4.97)-(3.6+0.4);
③按运算顺序计算;
④利用乘法分配律变成999×(1999+1);
⑤两个括号同时计算,最后算减.
点评:此题考查分数小数、分数四则混合运算,注意运算顺序,注意使用简便方法计算.
=(×-×)÷,
=(-)×8,
=×8,
=3;
②15.17-(3+4.97)-0.4,
=15.17-3.6-4.97-0.4,
=(15.17-4.97)-(3.6+0.4),
=10.2-4,
=6.2;
③÷+÷,
=×+×5,
=+,
=3;
④999×1999+999
=999×(1999+1),
=999×2000,
=1998000;
⑤(-)÷(×),
=÷,
=×,
=.
分析:①把0.7×看做×,0.11×看做×,先算括号里的,再算括号外面÷0.125看做除以;
②把原算式变成15.17-3.6-4.97-0.4,然后变成(15.17-4.97)-(3.6+0.4);
③按运算顺序计算;
④利用乘法分配律变成999×(1999+1);
⑤两个括号同时计算,最后算减.
点评:此题考查分数小数、分数四则混合运算,注意运算顺序,注意使用简便方法计算.
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