Tính bằng cách thuận tiện a) 2 450 × 34 + 34 × 1 548 – 2 998 × 34 b) 12 540 × 156 + 12 540 × 230 – 12 540 × 286

a) 2 450 × 34 + 34 × 1 548 – 2 998 × 34

= 34 × (2 450 + 1 548 – 2 998)

= 34 × 1 000

= 34 000

b) 12 540 × 156 + 12 540 × 230 – 12 540 × 286

= 12 540 × (156 + 230 – 286)

= 12 540 × 100

= 12 540

c) 578 × 136 + 192 × 136 + 136 × 230

= 136 × (578 + 192 + 230)

= 136 × 1 000

= 136 000

d) 69 × 57 + 57 × 31 + 49 × 34 + 66 × 49

= 57 × (69 + 31) + 49 × (34 + 66)

= 57 × 100 + 49 × 100

= 100 × (57 + 49)

= 100 × 106

= 10 600