Question

18．計算下面各題．
20×$\frac{2}{5}$
$\frac{1}{3}$+$\frac{3}{8}$
$\frac{8}{21}$×$\frac{7}{16}$
$\frac{1}{6}$+$\frac{2}{5}$
$\frac{3}{4}$×1$\frac{1}{3}$
$\frac{3}{4}$×12．

Answer 1

分析 根據(jù)分數(shù)的加減乘除法的計算方法計算．

解答 解：①20×$\frac{2}{5}$=8

②$\frac{1}{3}$+$\frac{3}{8}$
=$\frac{8}{24}+\frac{9}{24}$
=$\frac{17}{24}$

③$\frac{8}{21}$×$\frac{7}{16}$=$\frac{1}{6}$

④$\frac{1}{6}$+$\frac{2}{5}$
=$\frac{5}{30}+\frac{12}{30}$
=$\frac{17}{30}$

⑤$\frac{3}{4}$×1$\frac{1}{3}$
=$\frac{3}{4}×\frac{4}{3}$
=1

⑥$\frac{3}{4}$×12=9

點評 計算分數(shù)除法要變成乘法，再按照分數(shù)乘法計算，算分數(shù)的乘法要先約分再計算．