Tính nhẩm: 3× 4 = 4 × 3 = 2 × 6 = 3 × 6 3 × 5 = 5 ×3 = 2 × 7 = 2 × 9 = 5 × 6 = 5 × 8
Giải thích
3× 4 = 12 4 × 3 = 12 2 × 6 = 12 3 × 6 = 12 | 3 × 5 = 15 5 ×3 = 15 2 × 7 = 14 2 × 9 = 18 | 5 × 6 = 30 5 × 8 = 40 5 × 4 = 20 5 × 7 = 35 | 3 × 8 = 24 3 × 9 = 27 5 × 9 = 45 4 × 9 = 36 |