Question

Tính nhanh 

2.31.12+4.6.42+8.27.3

13.9

39.101

213-98

28.25

600:25

(1200-24):12

Answer 1

2.31.12+4.6.42+8.27.3

= ( 2 . 12 ) . 31 + 24 . 42 + ( 8.3 ) . 27

= 24 . 31 + 24 . 42 + 24 . 27

= 24 . ( 31 + 42 + 27 )

= 24 . 100 

= 2400

Answer 2

13 . 9 = 13 . ( 10 - 1 ) = 13 . 10 - 13 = 130 - 13 = 117

39 . 101 = 39 . ( 100 + 1 ) = 39.100 + 39 = 3900 + 39 = 3939

28 . 25 = 7 . 4 . 25 = 7 . ( 4 . 25 ) = 7 . 100 = 700