Tính bằng hai cách (theo mẫu): a) 4 × 6 × 9 b) 5 × 8 × 2

a) 4 × 6 × 9

Cách 1:

4 × 6 × 9 = (4 × 6) × 9 = 24 × 9 = 216

Cách 2:

4 × 6 × 9 = 4 × (6 × 9) = 4 × 54 = 216

b) 5 × 8 × 2

Cách 1:

5 × 8 × 2 = (5 × 8) × 2 = 40 × 2 = 80

Cách 2:

5 × 8 × 2 = 5 × (8 × 2) = 5 × 16 = 80

c) 7 × 3 × 5

Cách 1:

7 × 3 × 5 = (7 × 3) × 5 = 21 × 5 = 105

Cách 2:

7 × 3 × 5 = 7 × (3 × 5) = 7 × 15 = 105

d) 2 × 9 × 8

Cách 1:

2 × 9 × 8 = (2 × 9) × 8 = 18 × 8 = 144

Cách 2:

2 × 9 × 8 = 2 × (9 × 8) = 2 × 72 = 144