口算。                                                                                                                                      

84÷4＝	300÷5＝	96÷3＝	3000÷6＝
50×40＝	47×20＝	11×70＝	17×3＝
0÷40＝	1.9+0.5＝	1.2﹣0.3＝	7.3+0.7＝