The questions and answers of oral calculation in the second volume of mathematics in the fourth grade of primary school are as follows:

First, 640÷80= 8.

Second, 15×5= 75.

Three. 23×3= 69

Four. 12×2×5= 120

Five, 480÷80= 6

Six, 16×5= 80

Seven. 27×3= 8 1

Eight, 90÷ 15= 6

Nine, 48÷4= 12

X.640÷ 16=40

Eleven, 39÷3= 13

12.24×20= 480

Thirteen. 32×3= 96

Fourteen, 48÷ 16= 3

Fifteen. 12×8=96

16.27×3= 8 1

Seventeen, 5614 = 4

Eighteen, 24÷8=3

Nineteen, 14×2=28

Twenty, 83-45 = 38

2 1, 560÷80=7

Twenty-two, 96÷24=4

23,40 ÷ 20 = 2

24.40×30= 1200