Question

20．在橫線上填上“＞”“＜”或“=”
$\frac{2}{9}$×1=$\frac{2}{9}$   
$\frac{4}{5}$＞$\frac{4}{5}$×$\frac{1}{4}$
$\frac{3}{4}$×$\frac{3}{4}$＜$\frac{3}{4}$  
$\frac{6}{7}$×$\frac{7}{6}$=$\frac{3}{2}$×$\frac{2}{3}$
24×$\frac{5}{12}$＜$\frac{7}{12}$×24  
20×$\frac{1}{4}$＞$\frac{1}{5}$×20．

Answer 1

分析 一個數（0除外）乘小于1的數，積小于這個數；一個數（0除外）乘大于1的數，積大于這個數；據此解答．

解答 解：$\frac{2}{9}$×1=$\frac{2}{9}$   
$\frac{4}{5}$＞$\frac{4}{5}$×$\frac{1}{4}$
$\frac{3}{4}$×$\frac{3}{4}$＜$\frac{3}{4}$  
$\frac{6}{7}$×$\frac{7}{6}$=$\frac{3}{2}$×$\frac{2}{3}$
24×$\frac{5}{12}$＜$\frac{7}{12}$×24 
20×$\frac{1}{4}$＞$\frac{1}{5}$×20
故答案為：=，＞，＜，=，＜，＞．

點評 此題考查了不用計算判斷因數與積之間大小關系的方法．