题目内容
6.计算下列各题,怎样简便怎样算.105×13-1890÷18 | [$\frac{1}{2}$-($\frac{3}{4}$-$\frac{3}{5}$)]÷$\frac{7}{10}$ | 25×$\frac{3}{5}$+2.75÷$\frac{5}{3}$ |
27.4-52.8÷(1.9+2.1) | (0.125×8-0.5)×4 | 9.25×9.9+0.925 |
分析 (1)先同时计算乘法和除法,再算减法;
(2)先算小括号里面的减法,再算中括号里面的减法,最后算括号外的除法;
(3)先算乘法和除法,再算加法;
(4)先算小括号里面的加法,再算括号外的除法,最后算括号外的减法;
(5)先算小括号里面的乘法,再算小括号里面的减法,最后算括号外的乘法;
(6)先根据积不变规律变形,再根据乘法分配律简算.
解答 解:(1)105×13-1890÷18
=1365-105
=1260;
(2)[$\frac{1}{2}$-($\frac{3}{4}$-$\frac{3}{5}$)]÷$\frac{7}{10}$
=[$\frac{1}{2}$-$\frac{3}{20}$]÷$\frac{7}{10}$
=$\frac{7}{20}$÷$\frac{7}{10}$
=$\frac{1}{2}$;
(3)25×$\frac{3}{5}$+2.75÷$\frac{5}{3}$
=25×$\frac{3}{5}$+2.75×$\frac{3}{5}$
=15+1.65
=16.65;
(4)27.4-52.8÷(1.9+2.1)
=27.4-52.8÷4
=27.4-13.2
=14.2;
(5)(0.125×8-0.5)×4
=(1-0.5)×4
=0.5×4
=2;
(6)9.25×9.9+0.925
=9.25×9.9+9.25×0.1
=9.25×(9.9+0.1)
=9.25×10
=92.5.
点评 本题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.
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