Question

[Pham Trong Bach]

Tính bằng hai cách theo mẫu:

Mẫu: 452 × 39 = 452 × (30 + 9)

= 452 × 30 + 452 × 9

= 13560 + 4068 = 17628

452 × 39 = 452 × (40 – 1 )

= 452 × 40 + 452 × 1

= 18080 - 452 = 17628

a) 896 × 23

b) 547 × 38

Answer 1

[Cao Minh Tâm]

a) 896 × 23 = 896 × (20 + 3)

= 896 × 20 + 896 × 3

= 17920 + 2688

= 20608

896 × 23 = 896 × (24 – 1 )

= 896 × 24 – 896 × 1

= 211504 – 896

= 20608

b) 547 × 38 = 547 × (30 + 8)

= 547 × 30 + 547 × 8

= 20786

547 × 38 = 547 × (39 – 1)

= 547 × 39 - 547 × 1

= 21333 – 547

= 20786