Tính bằng cách thuận tiện: a) 35 .18 – 5 . 7 . 28 b) 45 – 5 . (12 + 9) c) 24 . (16 – 5) – 16 . (24 - 5) d) 29 . (19 – 13) – 19 . (29 – 13)

2 câu trả lời

`a)35 .18 – 5 . 7 . 28`

`= 35.18 - 35.28`

`= 35.(18-28)`

`=35.(-10)`

`= -350`

`b)45 – 5 . (12 + 9)`

`=45 - 5.12 -5.9`

`=45 - 60 -45`

`=-60`

`c) 24 . (16 – 5) – 16 . (24 - 5)`

`=24.16 - 24.5 -16.24 + 16.5`

`=-120 + 80`

`=-40`

`d)29 . (19 – 13) – 19 . (29 – 13)`

`= 29.19 - 13.29 - 19.29 + 19.13`

`=13.(-29 + 19)`

`=13.(-10)`

`=-130`

Tính bằng cách thuận tiện :

a) `35 . 18 - 5 . 7 . 28`

`= 35 . 18 - ( 5 . 7 ) . 28`

`= 35 . 18 - 35 . 28`

`= 35.(18-28)`

`=35.(-10)`

`=-350`

b) `45 - 5 . ( 12 + 9 )`

`=45-5.12-5.9`

`=45-60-45`

`=45-45-60`

`=0-60`

`=-60`

c) `24 . ( 16 - 5 ) - 16 .( 24 -5 )`

`=24 . 16 - 24.5 - 16. 24 - 16.5`

`=-120+80`

`=-40`

d) `29.(19-13)-19.(29-13)`

`=29.19-29.13-19.29-13`

`=13.(-29+19)`

`=13.(-10)`

`=-130`