题目内容
3.简便计算.$\frac{2}{3}$×$\frac{4}{7}$×$\frac{3}{10}$ | ($\frac{2}{9}$+$\frac{3}{8}$)×72 | ($\frac{3}{4}$+$\frac{3}{7}$)×7×4 |
$\frac{5}{12}$×13-$\frac{5}{12}$ | $\frac{11}{13}$×$\frac{6}{19}$+$\frac{6}{13}$×$\frac{8}{19}$ | 17×$\frac{29}{30}$ |
分析 (1)根据乘法交换律进行计算;
(2)、(3)、(4)、(5)、(6)根据乘法分配律进行计算.
解答 解:(1)$\frac{2}{3}$×$\frac{4}{7}$×$\frac{3}{10}$
=$\frac{2}{3}$×$\frac{3}{10}$×$\frac{4}{7}$
=$\frac{1}{5}$×$\frac{4}{7}$
=$\frac{4}{35}$;
(2)($\frac{2}{9}$+$\frac{3}{8}$)×72
=$\frac{2}{9}$×72+$\frac{3}{8}$×72
=16+27
=43;
(3)($\frac{3}{4}$+$\frac{3}{7}$)×7×4
=$\frac{3}{4}$×7×4+$\frac{3}{7}$×7×4
=21+12
=33;
(4)$\frac{5}{12}$×13-$\frac{5}{12}$
=$\frac{5}{12}$×(13-1)
=$\frac{5}{12}$×12
=5;
(5)$\frac{11}{13}$×$\frac{6}{19}$+$\frac{6}{13}$×$\frac{8}{19}$
=$\frac{6}{13}$×$\frac{11}{19}$+$\frac{6}{13}$×$\frac{8}{19}$
=$\frac{6}{13}$×($\frac{11}{19}$+$\frac{8}{19}$)
=$\frac{6}{13}$×1
=$\frac{6}{13}$;
(6)17×$\frac{29}{30}$
=17×(1-$\frac{1}{30}$)
=17×1-17×$\frac{1}{30}$
=17-$\frac{17}{30}$
=16$\frac{13}{30}$.
点评 考查了运算定律与简便运算,灵活运用所学的运算定律进行简便计算.