Tính nhẩm. 7 × 50 × 20

a) 7 × 50 × 20 = .............................

   b) 40 × 3 × 50 = .............................

c) 80 × 1000 × 4 = .............................

   d) 3 × 60 × 500 = .............................

a) 7 × 50 × 20

= 7 × (50 × 20)

= 7 × 1 000

= 7 000

   b) 40 × 3 × 50

   = (40 × 50) × 3

   = 2 000 × 3

   = 6 000

c) 80 × 1000 × 4

= 80 000 × 4

= 320 000

   d) 3 × 60 × 500

   = 3 × (60 × 500 )

   = 3 × 30 000

   = 90 000