题目内容

9.怎样算简便就怎样算
$\frac{2}{9}$-$\frac{7}{16}$×$\frac{2}{9}$ $\frac{9}{32}$÷$\frac{3}{4}$×$\frac{7}{16}$÷$\frac{1}{4}$           24×$\frac{5}{7}$×$\frac{7}{12}$($\frac{8}{9}$+$\frac{4}{27}$)×27
[1-($\frac{1}{4}$+$\frac{3}{8}$)]÷$\frac{1}{4}$         56×$\frac{1}{57}$  87×$\frac{3}{86}$

分析 (1)(4)(6)(7)利用乘法分配律简算;
(2)把除法改为连乘约分计算即可;
(3)利用乘法交换律简算即可;
(5)先算加法,再算减法,最后算除法.

解答

解:(1)$\frac{2}{9}$-$\frac{7}{16}$×$\frac{2}{9}$ 
=(1-$\frac{7}{16}$)×$\frac{2}{9}$ 
=$\frac{9}{16}$×$\frac{2}{9}$
=$\frac{1}{8}$;

(2)$\frac{9}{32}$÷$\frac{3}{4}$×$\frac{7}{16}$÷$\frac{1}{4}$   
=$\frac{9}{32}$×$\frac{4}{3}$×$\frac{7}{16}$×4
=$\frac{21}{32}$;  

(3)24×$\frac{5}{7}$×$\frac{7}{12}$
=24×$\frac{7}{12}$×$\frac{5}{7}$
=14×$\frac{5}{7}$
=10;

(4)($\frac{8}{9}$+$\frac{4}{27}$)×27
=$\frac{8}{9}$×27+$\frac{4}{27}$×27
=24+4
=28;

(5)[1-($\frac{1}{4}$+$\frac{3}{8}$)]÷$\frac{1}{4}$ 
=[1-$\frac{5}{8}$]÷$\frac{1}{4}$ 
=$\frac{3}{8}$×4
=$\frac{3}{2}$;

(6)56×$\frac{1}{57}$  
=(57-1)×$\frac{1}{57}$  
=57×$\frac{1}{57}$-1×$\frac{1}{57}$  
=1-$\frac{1}{57}$  
=$\frac{56}{57}$;

(7)87×$\frac{3}{86}$
=(86+1)×$\frac{3}{86}$
=86×$\frac{3}{86}$+1×$\frac{3}{86}$
=3+$\frac{3}{86}$
=3$\frac{3}{86}$.

点评 分数四则混合运算的关键是抓住运算顺序,正确按运算顺序计算,适当利用运算定律简算.

练习册系列答案
相关题目

违法和不良信息举报电话:027-86699610 举报邮箱:58377363@163.com

精英家教网