Tính bằng cách thuận tiện a) 25 × 15 × 4                                             b) 8 × 50 × 2 × 125

a) 25 × 15 × 4

= (25 × 4) × 15

= 100 × 15

= 1 500

b) 8 × 50 × 2 × 125

= (8 × 125) × (50 × 2)

= 1 000 × 100

= 100 000

c) 2 578 × 4 × 500

= 2 578 × 2 × 2 × 500

= 2 578 × 2 × (2 × 500)

= 5 156 × 1 000

= 5 156 000

d) 5 × 249 × 2

= (5 × 2) × 249

= 10 × 249

= 2 490

e) 125 × 40 × 8 × 250

= (125 × 8) × (40 × 250)

= 1 000 × 10 000

= 10 000 000