Question

Tính nhanh

a, 6100 + 2900 =

b, 7825 + 1075 =

c, 285 + 285 + 285 + 285 =

d, 2345 + 1745 =

Answer 1

a, 6100 + 2900

 = (6000 + 2000) + (100 + 900)

 = 8000 + 1000 = 9000

b, 7825 + 1075

 = (7000 + 1000) + 800 + (25 + 75)

 = 8000 + 800 + 100

 = 8900

c, 285 + 285 + 285 + 285 = 285 × 4 = 1140

d, 2345 + 1745

 = (2000 + 1000) + (300 + 700) + (45 + 45)

 = 3000 + 1000 + 90

 = 4090