一、口算。
$62 - 41 =$ $81×5 =$ $98÷7 =$
$36÷2 =$ $47 + 46 =$ $29×3 =$
$250÷5 =$ $161 - 78 =$ $172×2 =$
$16×40 =$ $856÷8 =$ $40×45 =$
$570 + 80 =$ $990÷9 =$ $131×3 =$
$204÷3 =$ $5×301 =$ $13×50 =$
$35×30 =$ $393÷3 =$ $195÷3 =$
$120×2 =$ $18×40 =$ $27×60 =$

一、21 405 14
18 93 87
50 83 344
640 107 1800
650 110 393
68 1505 650
1050 131 65
240 720 1620

二、怎样比较$\dfrac{1}{5}$和$\dfrac{1}{4}$的大小？ 看图填一填。



因为$\dfrac{(\_\_\_\_\_\_)}{20} ◯ \dfrac{(\_\_\_\_\_\_)}{20}$，所以$\dfrac{1}{5} ◯ \dfrac{1}{4}$。

二、2 3 4
2 3 4 5
4 ＜ 5 ＜