a 27 . 75 + 25 . 27 - 150

= 27 . ( 75 + 25 ) - 150

= 27 . 100 - 150

= 2700 - 150

2550

b ) 12 : { 390 :  [ 500 - ( 125 + 35 . 7 ) ] }

= 12 : { 390 : [ 500 - ( 125 + 245 ) ] }

= 12 : { 390 : [ 500 - 370 ] }

= 12 : { 390 : 130 }

= 12 : 3

= 4

a) 2550 

b) 4

a 27 . 75 + 25 . 27 - 150

= 27 . ( 75 + 25 ) - 150

= 27 . 100 - 150

= 2700 - 150

2550

b ) 12 : { 390 :  [ 500 - ( 125 + 35 . 7 ) ] }

= 12 : { 390 : [ 500 - ( 125 + 245 ) ] }

= 12 : { 390 : [ 500 - 370 ] }

= 12 : { 390 : 130 }

= 12 : 3

= 4

a) 27.75+26.27-150=27(75+25)-150

                           = 2700-150

                            = 2550

b) = 12: {390:[500-370]

= 12:{390:130}

=12:3

=4

a)27.75+25.27-150

=27.(75+25)-150

=27.100-150

=2700-150

=2550

b)12:{390:[500-(125+35.7)]}

=12:{390:[500-(125+245)]}

=12:{390:[500-370]}

=12:{390:130}

=12:3

=4

a, 27.75+ 25.27-150                                     b,

= 27.(75 +25) -150

=27.100-150

=2700-150

=2550

a} 2550

b} 4

a) 27 . 75 + 25 . 27 - 150

= 27 . ( 75 + 25 ) - 150

= 27 . 100 - 150

= 2700 - 150

= 2550

b) 12 : { 390 : [ 500 - ( 125 + 35 . 7 ]}

= 12 : { 390 : [ 500 - ( 125 + 245 )]}

= 12 : { 390 : [ 500 - 370 ]}

= 12 : { 390 : 130 }

= 12 : 3

= 4

a) 27 . 75 + 25 . 27 - 150

= 27 . ( 75 + 25 ) - 150

= 27 . 100 - 150

= 2700 - 150

= 2550

b) 12 : { 390 : [ 500 - ( 125 + 35 . 7 ]}

= 12 : { 390 : [ 500 - ( 125 + 245 )]}

= 12 : { 390 : [ 500 - 370 ]}

= 12 : { 390 : 130 }

= 12 : 3

= 4

a) 27 . 75 + 25 . 27 - 150 = 2025 + 675 - 150 = 2700 - 150 = 2550.

Lưu ý. Có thể dùng tính chất phân phối của phép nhân đối với phép cộng để nhẩm:

27 . 75 + 25 . 27 - 150 = 27 . (75 + 25) - 150 = 27 . 100 - 150 = 2700 - 150 = 2550.

b) 12 : {390 : [500 - (125 + 35 . 7)]} = 12 : {390 : [500 - (125 + 245)]}

= 12 : [390 : (500 - 370)] = 12 : (390 : 130) = 12 : 3 = 4.

12 : {390 : [500 – (125 + 35.7)]}

= 12 : {390 : [500 – (125 + 245)]}

= 12 : {390 : [500 - 370]}

= 12 : {390 : 130}

= 12 : 3

= 4

a)80-[130-(12-40)²]         b)27.75+25.27-150             c)12:{390:[500-(125+35.7)]}

=80-[130-(-28)²]             =27.(75+25)-150                 =12:{390:[500-(125+245)]}

=80-[130-784]                =27.100-150                       =12:{390:[500-370]}

=80-(-654)                     =2700-150                          =12:{390:130}

=80+654                       =2550                                =12:3

=734                                                                      =4

Nhớ **** thanks so much^__^

a) \(27\cdot75+25\cdot27-150\)

\(=27\cdot\left(75+25\right)-150\)

\(=27\cdot100-150\)

\(=2700-150\)

\(=2550\)

b) \(12:\left\{390:\left|500-\left(125+35\cdot7\right)\right|\right\}\)

\(=12:\left\{390:\left|500-\left(125+245\right)\right|\right\}\)

\(=12:\left\{390:\left|500-370\right|\right\}\)

\(=12:\left\{390:130\right\}\)

\(=12:3\)

\(=3\)

a) 27.(75+25)-150=27.100-150=2550

a,3900.                     b,4

a)=27.(75+25)-150=27.100-150=2700-150=2550

b)=12:[390:(500-125-245)]=12:(390:130)=12:3=4

he he