口算:
2×4= 20 × 4= 200 × 4= 6 × 3= 60 ×3= 600 ×3= 40 ×8= 300 ×6= 20 ×6= 50 ×4= 200 ×3= 400 ×2= 30 ×5= 90 ×7= 50 ×9= 20 ×7= 6 ×50= 500 ×8=
