一、口算。
$80 + 9 =$ $10 + 60 =$ $64 - 60 =$
$85 - 5 =$ $38 - 8 =$ $2 + 80 =$
$3 + 60 =$ $9 + 50 =$ $60 - 40 =$
$35 - 30 =$ $45 - 5 =$ $70 + 6 =$
$6 + 50 =$ $20 + 50 =$ $58 - 8 =$
$90 - 70 =$ $43 - 40 =$ $50 + 4 =$
$4 + 30 =$ $80 + 7 =$ $79 - 70 =$
$32 - 30 =$ $92 - 90 =$ $4 + 90 =$
$70 + 7 =$ $5 + 60 =$ $57 - 50 =$
$80 - 20 =$ $61 - 60 =$ $80 + 6 =$

一、89 70 4 80 30 82 63 59 20 5 40 76 56 70 50 20 3 54 34 87 9 2 2 94 77 65 7 60 1 86

二、在$◯$里填“+”或“-”。
$60◯6 = 66$ $33◯30 = 3$ $27 = 7◯20$
$82◯2 = 80$ $30◯50 = 80$ $30 = 38◯8$
$70◯60 = 10$ $90◯2 = 92$ $4 = 84◯80$

二、+ - + - + - - + -

+ - + - + - - + -