题目内容
14.怎样简便就怎样算$2\frac{1}{2}$×6.6+2.5×$6\frac{3}{5}$
$\frac{4}{5}$+$9\frac{4}{5}$+$99\frac{4}{5}$+$999\frac{4}{5}$+$9999\frac{4}{5}$
1993÷1993$\frac{1993}{1994}$
7$\frac{5}{6}$+3$\frac{9}{10}$+2$\frac{1}{6}$+6.1.
分析 (1)根据乘法分配律进行简算;
(2)根据加法交换律和结合律进行简算;
(3)把带分数化成假分数,再计算;
(4)根据加法交换律和结合律进行简算.
解答 解:(1)$2\frac{1}{2}$×6.6+2.5×$6\frac{3}{5}$
=$2\frac{1}{2}$×6.6+2.5×6.6
=($2\frac{1}{2}$+2.5)×6.6
=5×6.6
=33;
(2)$\frac{4}{5}$+$9\frac{4}{5}$+$99\frac{4}{5}$+$999\frac{4}{5}$+$9999\frac{4}{5}$
=($\frac{1}{5}$+$\frac{1}{5}$+$\frac{1}{5}$+$\frac{1}{5}$)+$9\frac{4}{5}$+$99\frac{4}{5}$+$999\frac{4}{5}$+$9999\frac{4}{5}$
=($9\frac{4}{5}$+$\frac{1}{5}$)+($99\frac{4}{5}$+$\frac{1}{5}$)+($999\frac{4}{5}$+$\frac{1}{5}$)+($9999\frac{4}{5}$+$\frac{1}{5}$)
=10+100+1000+10000
=11110;
(3)1993÷1993$\frac{1993}{1994}$
=1993÷$\frac{1993×1994+1993}{1994}$
=1993÷$\frac{1993×(1994+1)}{1994}$
=1993÷$\frac{1993×1995}{1994}$
=1993×$\frac{1994}{1993×1995}$
=$\frac{1994}{1995}$;
(4)7$\frac{5}{6}$+3$\frac{9}{10}$+2$\frac{1}{6}$+6.1
=(7$\frac{5}{6}$+2$\frac{1}{6}$)+(3$\frac{9}{10}$+6.1)
=10+10
=20.
点评 考查了运算定律与简便运算,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.